"There is no such thing as a 'best opening.' Each player should choose an opening that attracts him. Some players are looking for a gambit as White, others for Black gambits. Many players that are starting out (or have bad memories) want to avoid mainstream systems, others want dynamic openings, and others want calm positional pathways. It’s all about personal taste and personal need.
For example, if you feel you’re poor at tactics you can choose a quiet positional opening (trying to hide from your weakness and just play chess), or seek more dynamic openings that engender lots of tactics and sacrifices (this might lead to more losses but, over time, will improve your tactical skills and make you stronger)." - IM Jeremy Silman (January 28, 2016)
https://www.chess.com/article/view/opening-questions-and-a-dream-mate
Best opening defence for black
I think it is common advice that one start with the sort of openings discussed in books like First Steps: 1 e4 e5 and First Steps: Queen's Gambit.
https://www.newinchess.com/media/wysiwyg/product_pdf/7790.pdf
https://www.newinchess.com/media/wysiwyg/product_pdf/7652.pdf
Might be a good idea to start with Discovering Chess Openings.
https://web.archive.org/web/20140627114655/http://www.chesscafe.com/text/hansen91.pdf

I'm playing the Philidor as black. It's solid, dynamic, and not a billion different variation like with the Sicilian. This is the main line that I play: 1. e4 d6 2. d4 Nf6 3. Nc3 Nbd7 4. Nf3 e5 5. Bc4 Be7 with 0-0 and c6 to follow.

I think it is common advice that one start with the sort of openings discussed in books like First Steps: 1 e4 e5 and First Steps: Queen's Gambit.
https://www.newinchess.com/media/wysiwyg/product_pdf/7790.pdf
https://www.newinchess.com/media/wysiwyg/product_pdf/7652.pdfi
i kniw those, thanks anyways

I'm playing the Philidor as black. It's solid, dynamic, and not a billion different variation like with the Sicilian. This is the main line that I play: 1. e4 d6 2. d4 Nf6 3. Nc3 Nbd7 4. Nf3 e5 5. Bc4 Be7 with 0-0 and c6 to follow.
I look into thx

At your level, https://en.wikipedia.org/wiki/Open_Game
At higher levels, https://en.wikipedia.org/wiki/Sicilian_Defence,_Najdorf_Variation

Of course what you should really try to improve is your ability to find winning combinations in your games. A great book on tactics is Common Chess Pattern, available in Chessable for 9,99. The book has 725 exercises. I worked intensively with this book in the last 3 weeks and I memorised most of these puzzles already. The great thing about Chessable is that you learn using spaced repetition. This means that puzzles that you get right you will review less frequently than puzzles that you get wrong.
If you work seriously with this book (at least 30 minutes per day during 2 or 3 months), you will get at least 1200 in chess.com. You should however analyse your games to be able to learn from your mistakes. And play rapid instead of blitz, of course.
Good luck!
What is the best? I just want to hear your opinions