@Rodrigo-Moraes, just by making this forum post you've shown clear dedication and a thirst to improve- that itself is deserving of an applaud 👏.
Before giving you way too many tips, let me introduce myself. I'm a high schooler in America that's been playing for almost 3 years now (not including learning the game when I was around 7). I knew nothing other than the rules when I started, and my blitz dropped down to 200 elo. Slowly but surely, and over 4000 games later, I'm over 1500 rapid, and aiming for the stars. I'm also fully self-taught. I've never had a coach, and only bought one book- all others I use are pdfs I find on the internet. I'm not in a chess club or anything either, it's just a lot of hard work and dedication.
First off, don't bully yourself. 600 isn't as bad as you think it is- just around the average rating. Don't make yourself feel worse just because you've played more, either. Playing does nothing except impact your rating- only reviewing your games and learning from them impacts your strength. Don't pay attention to your rating, pay attention to your strength. Get stronger, your rating will follow. Change of mindset → change of habits → change of strength → change of rating.
Now for my tips on everything you need to get to 1000 elo:
1. Become a puzzle maniac. You mentioned having a puzzle rating of 1400. That's good, but not good enough. I am a firm believer that your puzzle rating should be 1000 higher than your true rating. This shows your gaps in tactics compared to your opponents- you likely aren't grabbing the fruits your opponents leaves unguarded (or underguarded!). You're a diamond member (something I've never had), so you can do as many puzzles as you want. Don't do 100s a day or anything, but do say 10 a day (keeps the misses away 
). This should help you become constant in noticing opportunities- whether it's a hanging piece, opportunity for a fork, skewer, pin, discovered attack, mate in 1, 2, or 3, you name it! Becoming a master at these greatly impacts your strength (notice, not your rating, but that will follow!), as even I still blunder a pawn or piece sometimes (and less commonly, my opponents as well)!
2. Solo Chess Wins. Who knew this simple minigame was so effective! In fact, it's one of the things that really helped me to boost my rating! Not really helpful past 1000 elo, but it's an amazing tool for board visualization and basic calculation skills! This not only helps heal some problems, but it sets up an amazing foundation that you can use up to the master level! Seeing everything on the board and being able to calculate different lines is a tool everybody uses, and it separates good from great! But quick tip: don't do 15 and think it's too easy, make sure to go as far as you can, and think them out, don't just blindly move- that ruins the whole point.
3. Play (and review!)!!! The number 1 tool for any improver. Not only is it the only way to boost your elo, it's also the only way to see if you've grown (in strength!)! This is especially important for losses- something went wrong. There are 3 kinds of mistakes: common errors, strategic errors, and preparation errors.
Common errors: these are the most common at lower levels, and the ones that are hardest to get rid of. This includes hanging pieces, allowing tactics, and hanging mate. These are unfixable, because there's no thought process error or preparation errors to cure. You just "simply hung a piece". Nothing you can do about. Just have to work on board visualization and being more vigilant.
Strategic errors: These aren't really important for you to know until you're closer to 1400 elo, but they can be problematic at lower elos as well. These are errors in your ideas- "I want to take over the d-file with my rook", but no that's bad. "I think opening up this diagonal would be beneficial", but it's not. These are curable by training your mind to come up with the right ideas, and creating a mental list of the right ideas- especially in the pawn structures that arise from your opening. They can also occur when you're attacking (more important part for you)- "I think I should attack the king with this knight", but no, that piece is a crucial defender and you're about to get mated yourself. "I should take the h-pawn and then mate on g7", well you gave the king time to escape, you should have taken the g-pawn and mated on h7. Notice how these are patterns- easily fixable.
Preparation errors: not important for you at all, but this is when your opening prep is wrong. The most easily fixed since you can just tweak your prep.
All right that was a lot of yapping, but honestly I hope it helped. The main thing is just training your brain to make sure you don't hang pieces/allow tactics, and drilling puzzles to improve your recognition of different tactics.
If you want some more tips, explanations, or just some help from a higher rated player, feel free to DM me. I'd feel free to help you out some until you get a bit better, say 1000 maybe 1200. I wish you the best of luck and again, congrats for stepping up and asking for help, it's hard to do and it's one of the best decision you'll make in your chess career.
I took the time to review your latest loss. From what i'm seeing your main issue is not using the time given to you. You may have great tactical knowledge or good calculation skills but if you're playing moves as quickly as you did in this game, it will be tough to see said opportunities.
The Solution: Slow down when playing your moves. Feel stuck and don't know what to do? Instead of pushing a pawn in under 5 seconds, can you find a good minor piece move? Is there a threat you need to address? I explain the position in the link but I will elaborate a bit here.
After every move from my opponent the questions I ask myself are the following:
1. Why did my opponent move that piece? what is it threatening? (Fork? A tactic?)
2. Any pieces that couldn't threaten anything before, now can they threaten something because of this move? (discovered attacks)
3. What piece did my opponent stop guarding that was guarded before?
4. Did moving that piece create any weaknesses in the position?
if you can answer all of these questions in under 5 seconds, great! But if not, finding the answers will prove beneficial to your gameplay. To be honest you probably don't need to ask question 3 or 4 a vast majority of the time (at your current elo anyway). Just asking question 1 and 2 to yourself should reduce the amount of blunders you have. If you see no threat you could safely ignore the threat or counterattack. However you can't go horribly wrong adhering to chess principles by developing your minor and major pieces to squares that help them these are generally squares that attack the centre of hold control over it.
The Conclusion: You played a 10 minute rapid and resigned your position at 7:51. You are given that time. You are allowed to use it. If you can't use that time effectively and timeout? That's ok we all had to crawl before we could walk, and walk before we could run. Asking the questions I outlined is essentially a skill that needs to be trained.
If after doing all this and you find yourself not being able to see the reason for your opponents moves and losing despite using your time? It highlights the real issue (not seeing tactics, poor caculation). I think therefore playing slower is a win win for improvement.
Hope this helps.
Wow, thank you so much it helped A LOT.
I remember this game, and you gave me a complete analysis this makes much more sense now.
Many times I get confused of what is the best square for my pieces, I follow a brazilian GM named Krikor who says he had a coach that says: "Chess is easy if you put your pieces in correct squares"
Time is vital, and I think many times I'm not aware of, tried to spend lots of time when doing puzzles and I already found it useful, when I try to see every possible checks in a given movement.
Thanks for your analysis there, it was lengendary.
you're welcome.