I play at lichess and I also recomend it, but another good free app I use for tactics exercises is chesstempo.
It is just my preference. I find the collection of problems better. Lichess exercises are taken from blitz games analyzed by Stockfish. They are fine and free, but sometimes the selection they do with code is not accurate for a human.
Why waste your money when you've got free video repository like Youtube.
Watch this video, i think this is perhaps the best video i've ever come across to learn chess.
Some applications on playstore will definitely come handy:
I would suggest LiChess. It is free (of charge and ads) and it has a website + android app. You can practice vs other opponents, solve tactic puzzles. They also have a learning section, where you can learn about simple strategic concepts.
Forget about becoming a professional. Do you know how many grandmasters there are that are working at minimum wage?
Play for fun instead.
You need to learn one opening really well and learn tactics along with playing endgames. Later, you can focus on pawn structures and positional play.
There are some other esoteric subjects but until you are GM level ...
There are four categories of chess books. Many books fall into several of these categories of course.
Annotated games collections
Tactics are the most essential, and give the most bang for the buck. There are plenty to choose from. I like the classic 1001 Winning Chess Sacrifices and Combinations by Fred Reinfeld. ...
Black is in check, so Black is forced to deal with that first.
Black can't move out of check and can't take the checking piece so their only option is to block it. If Black blocks it with the Queen (Qc6) then White can take their knight which ends the immediate checkmate threat and leaves White up on material.
If Black blocks it with the rook (Rc6) then ...
1...Qb2 is not a legal move because black is in check; 1...Rc6 blocks the check. Another alternative to block the check is 1...Qc6, but that would drop the knight on d3.
[FEN "k1r4r/p6p/5p2/3Q4/1R5P/PPqn4/3N1P2/1K1R4 b - - 1 1"]
1... Rc6 (1... Qc6 2. Qxd3)
A first book should give you a very broad understanding. While some books that cover specific areas (like tactics books) might be excellent 2nd or 3rd books, they don't cover the entire game. Other books (like Chernev's) give great examples but don't explain the fundamentals of getting there. That would be like getting a collection of brilliantly solved math ...
You don't mention whether you prefer studying chess with books or at the computer, so I'll toss a couple of ideas at you for both.
Russia Chess House has some good beginning tactics books (Chess School 1a and 1b) with a thousand or so basic positions, showing some elementary checkmates and basic tactics. They make a pretty good starting out resource, ...