Improving my skills is getting harder I am new to chess and I am playng mostly online at sites like chess.com. Now I have a rate around 800, so it is still low, but my problem is that improving my skills is getting hard. The arrival to the rate 800 has been quite quick, but now I feel like I am stucking often to the same moves and the same way of reasonings.

How could I improve my skills? And most of all how can I improve my mental elasticity in playing chess in order to be a better player?

Thanks in advance.
It really depends on whether you are willing to do the work, but I have tried this with people before, and it has worked extremely well. Most weaker players are initially weak because they lose material so often and easily.

First, I believe strongly in an immersion-type training program. If I give you 20 problems, and you get 100%, you only learned 20 problems. If I give you 150, and you only get a 66.6%, you still learned 100 problems, or five times what you did when you got only 20 problems. I firmly believe that the more you see in a short period of time, the more you will learn. In this case, I am advocating quantity over quality.

This is based on my own personal experience, and is based on my learning Russian in the Air Force. The first night, I got 20 words to learn, but by the end of 47 weeks, we got about 300 words every other night. I also had a friend, who was 38 at the time, and he went from 1000 to about 1850 on the Internet Chess Club in three months doing what I am about to recommend.

I am not a fan of the chess.com and other site tactics programs for a couple of reasons. First, they are checked by computers, and often take the computer route in the defense portion of the solution, rather than the human path. Second, they are not well grouped by theme.

I still love the grouping on the two Fred Reinfeld books, "1001 Brilliant Ways to Checkmate, 21st Century Edition" and "1001 Winning Chess Sacrifices and Combinations, 21st Century Edition".

You start with the 1001 checkmates book because the first chapter is queen sacrifices, so you have two big hints: Give up the queen, and checkmate. Now, I want you to try to do 50 per day (25 minimum though), spending no more than two minutes on each problem trying to figure it out. If you do not get it, just look at the answer, and play it out on a board, if necessary. You may not have gotten it right, but you have absorbed something. Write in pencil next to the diagram 1-5, with one being that you solved it easily, and five that you had no idea.

Go through the whole book at 50 per day. You can skip the last chapter on composed mates if you want. Do the same with the 1001 sacrifices book.

Now, you have read both, and have rated how easily you got them. Go back ans read the both books again in the same order. They are both grouped so well, that you will start to pick up on themes better than ever.

Funny, in early 2019, a new book, "The Woodpecker Method" came out, and recommends a very similar method to the one that I have been recommending for over 30 years.

I have found over the years that even guys, who are 2000-2100 over-the-board, are still not that great tactically, so keep doing this, and as you get better with your two original books, pick different tactics books for some variety. We never stop practicing that, and calculation, in general.

Of course, as you get better, there is a lot more to learn about opening pawn structures (search my other posts about this), and of course, the endgame.