Well, this has been mentioned to you before, but the answer is to hit the books and do some precise work and stop focusing on blitz so much.
I started with Nimzowitsch's My System when I was about 9 or 10. So it is NOT too complicated for the average amateur. The first three chapter of that book, in particular, are very good at explaining the basics of opening theory and middlegame strategy. (Develop your pieces and aim for the centre, basically).
But if a classic like that is too intimidating for you, go with Seirawan's books; they are written with the amateur in mind and he has a whole series. He starts at the very beginning.
Another good beginner's book is Lev Alburt's complete chess course.
Unless you take the trouble of going through the theory and working through problems with PRECISION, I'm afraid you'll never improve much.
As for the rating differences, Internet ratings aren't worth much; generally speaking, the smaller the pool of opponents, the harder it is to go up the rankings. The reason your Lichess rating is higher is there is much less competition there. Ratings are meaningless in an absolute sense; they depend on the pool of people you're in.
That's like saying: I came in 1st in the race!
Well, that phrase takes on a whole different meaning if a) You were playing pacer for a bunch of toddlers. or b) You were running the 100m at the Olympics.