Where do you search free Chess software, books,...?

For some good free courses, check out Chessable: https://www.chessable.com/courses/all/all/free/. An account is free and normally limited to 10 free courses, however, you can purchase more slots for money or save up by working on your other courses. I personally wouldn't recommend strategy courses in Chessable, but for theoretical sections (opening, endgame) and tactics it's great.

For free analysis, Arena (http://www.playwitharena.de/) is I best I think (though I mainly use paid Chessbase software myself).

For strategy, you don't really need serious study yet judging by your game. Follow principles of checking for tactics, focusing on the centre, developing your pieces and paying attention to (relatively) simple positional characteristics as pawn structure, open files for rooks, open diagonals for bishops and make sure your pieces maximize their potential activity.

https://www.chess.com/blog/RussBell/improving-your-chess-resources-for-beginners-and-beyond is also a great resource made by another member on this site. Worth checking out his entire blog, as there is some great information on that.

Also Youtube may be a good resource, but the risk there is always you find some bad video that happens to have a lot of views, rather than a hidden gem.

Check out Scribd...

https://www.chess.com/blog/RussBell/scribd-com-for-online-chess-book-reading

https://www.chess.com/blog/RussBell

Thanks Selwink !