how can i be better at chess?

Have a short opening repertoire for now, read the fundamentals of chess and try to stick with 'em! Solve puzzles, and watch more top-level games than you play! Play longer time formats, and if you get burnt out, do consider taking a break!

Improving Your Chess - Resources for Beginners and Beyond…

https://www.chess.com/blog/RussBell/improving-your-chess-resources-for-beginners-and-beyond

Not sure what level exactly you're at now, but I recommend highly these FIRST 2 books, and then a few others later as you go. (one is a 2 volume set):

1. Chess Fundamentals by JR Capablanca - superb book on all sorts of good principles and has game examples in it as well - available in many languages but the English or Spanish versions most common. Amazon carries it.
2. Understanding Chess Move by Move by John Nunn - also available on Amazon and other outlets. A very good series of example games, with some detailed analysis as well (more on this below). 
3. Paul Keres' Best Games, Volume 1 and 2 - by Egon Varnusz - Has examples (VERY excellent ones!) of games by the GM Paul Keres, and has good opening/game types categorized together with example games. VERY instructive! Again, Vol 1 and 2 available on Amazon, and other websites.
4. Paul Kerez and Alexander Kotov's: The Art of the Middlegame - this has examples of games with a good overall strategies as the openings progress. SUPERB information, but caveat/caution on this one is that it uses the older "descriptive" notation. Good to learn as there are many excellent Russian GM books and many others (see #5 as an option in lieu of #3, which also has this notation) and it is good to be able to work through these game examples to be a better player I think. #3 is one of the few examples of a very good book on an important phase in Chess games that concisely and lucidly covers the topic well, without getting too complex. May be a bit of a challenge for a newer chess player, but you can take your time through these. 
5. Also a classic and exceptional: The Most Instructive Games of Chess Ever Played, by Irving Chernev - this also uses the older notation (see below for examples) but has excellent pre-1950 games, with great examples (62 games total) of positions and use of pieces to achieve certain positions and wins. REALLY good also! 

Now for what I mean by older descriptive notation: There are TWO common versions of this, one is a more lengthy version and one is the abbreviated one. In the latter, it CAN at times be tricky to see a move because you HAVE to basically play it out on a board or computer manual screen to see the moves.

Descriptive notation - Wikipedia

The board at the right uses DESCRIPTIVE Notation. I would look through the Wkipedia link for more detail. However, I'll use a simple example:

If one was to move (as White) their Knight on the first move of an opening, they can go either Nc3 or Nf3. (also sometimes notated as Nb1-c3 or Ng1-f3, but usually the algebraic easier notation is used. To do this with Abbreviated descriptive notation, it would be QN-B3 (N-QB3), and QN-B3 (or N-KB3) - the assumption is the king's knight, for example, cannot go to "B3/bishop 3" other than on its respective side. If Black plays its first knight moves, these would be the SAME in descriptive notations, since the board is laid out to cover king/queen-sides for the squares. In Algebraic, we use the piece and its new square done as coordinates.

One more example. If I was to move e2-e4 (or just e4) as my opening move, and black does d7-d5 (or just d5), and then next move was to take the Black d-pawn:

1. e4 d5 2. exd5 ... in descriptive, this would be:

1. P-K4 P-Q4 2. PxP ... so the ambiguity is the PxP, only because UNLESS you follow all the moves, there may be some mild confusion at first until you work through these games done in that notation. good news is in those game books using the older notation, there's mid-game diagrams showing the pieces layout (usually also in other books too), and you can check whether the moves were correct. A great way to learn this system, as many excellent pre-1970 books use that notation, and it is good to understand this later. I usually work through my books with that older format by jotting (pencil) algebraic equivalent moves so later I just play the games out.

I suggest #1 and #2 as first choices, as they use modern notation and are great to learn from first, before trying to work through more complicated stuff.

Finally, the reason I suggest books first over say... YouTube videos, is that these can be used ANYWHERE, in private, or with a friend, and you do not need power/internet to do this, and you can study at your leisure as time permits. I also suggest first, if you get book #2, to work through it initially by making the moves (a few at a time) and just LOOK at the positions and ask WHY those moves were made, and where you THINK the next few might be. Sometimes, it is fairly obvious, sometimes not. Some moves in those games may even be errors played at the time, and the author suggests alternates. Don't initially get too hung up on the analyses at first, just move the pieces and see how the layout looks. Then, once you're feeling more confident, try moving the alternate choices to SEE how the new position(s) may have played out if done as per the author's choices. VERY instructive, and you can get a VERY LARGE amount of learning even out of 1-2 books.

I know that this reply is rather wordy, but I felt as a 5-decade+ player that I would do better to offer some great choices - study of the game is essential to being better. Be confident that taking things at YOUR pace is a good way to get better and have the new skills stay with you!

Good chess and good luck!

Rookium - Rm