Chess improvement

Hi, I've been working on my chess for a while, when I started taking chess slightly more seriously, my rating skyrocketed from 700-1200 and now I seem to be stuck at my current rapid rating, I've been doing everything I can to improve, watching chess lessons, analysing my games learning from master games and tactics but no matter what I try I haven't seen improvement for a while now, what should I do, and why haven't I been improving? 

@1
It is about tactics. Here is an example:
You neglect development and king safety.

With the weakening 8...f6? you open yourself to tactics along the diagonal h5-e8 to your king.
Just solidly developing a piece 8...Nh6 was fine.
With 11 Bf3?? instead of 11 f5 your opponent lets you back into the game
12...exd4? instead of the more solid, central 12...cxd4 allows your opponent the attack 13 f5
13...Nxd4?? instead of developing 13...Nh6 again allows the attack 14 f5
14...Nc6?? instead of the safe 14...b5 allows for the 4th time the win 15 f5, this time he plays it

Alright, thanks for your help, so should I be doing more tactics, or is there some other way to improve on my weaknesses here?

@3
Solving tactics puzzles is good.
However, in a real game nobody tells you there is a tactic or for which side.
In this game you did not miss any tactics for you, but you exposed your king to tactics 5 times.
You need to grow an awareness.

8...f6? is weakening, do not do that.
Especially if you are defending, develop pieces into play 8...Nh6, 13...Nh6.
Always play for the center: 12...cxd4, not 12...exd4??.
If you were white, would you have found 11 f5, 13 f5, 14 f5, 15 f5?
It is a bit of a problem with tactics puzzles: they present the puzzle from the winning side.

Alright, thanks a lot for your help!