It seems you like simplified positions. Try to trade down, probably, and get into a more simplified middle- or end-game.
How to beat the Jonas bot?

I do prefer simplified positions but stronger players generally don't trade down unless it improves their position somehow.

What’s Jonas’s rating?
EDIT — never mind, found out. What is your clubmate’s rating?
About the same strength as the bot. 1400 classical/1500 rapid.

I play out the openings entirely on general principles. The computer evaluation says I am slightly better but I never actually get a material advantage. Then I reach a middlegame position that feels like I have been transported into a new foreign land.

From what you've written I gather that your nemesis is a better player than you are, and that is the reason why he wins. Not a lot better, only a bit better, but even that can lead to lopsided results, see for instance the Carlsen - Nepo match.
Having a slightly better position out of the opening does not mean much, especially in blitz chess. Openings matter very little, blunders matter a lot. Try to not blunder, or at least blunder less.
The good thing is that you are improving rapidly, and your opponent presumably isn't. Just keep doing what you are doing, and in a few months you will be the better player.
Unfortunately I only play the free bots so far. However, if you post a typical game of yours against it, we could take a look.
For example, in your most recent game against Jonas, it looks like you missed the fact that his 14th move attacked your rook. Based on this, I think you need to make sure you see what your opponent's move is doing, and in particular what attacks he is making, before planning your move. If you'd seen his attack on your rook, you could have interposed your queen to offer a queen trade, for example.
https://www.chess.com/game/computer/2531863

I played him again and got a draw. Should've won but blundered the rook and pawns endgame. Jonas is definitely beatable but puts up a tough fight when behind.


[Site "Chess.com iPhone"]
[Date "2022.12.14"]
[Round "?"]
[White "matthewchau4"]
[Black "Jonas"]
[Result "1-0"]
[FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]
[WhiteElo "808"]
[BlackElo "1700"]
[Termination "matthewchau4 wins by Checkmate"]
1.e4 b6 2.d4 Bb7 3.Nc3 e6 4.e5 Ne7 5.Nf3 Nbc6 6.Bb5 Nb4 7.a3 Nbd5 8.Nxd5 Bxd5 9.O-O a6 10.Bd3 b5 11.b3 h6 12.c4 Bc6 13.Qe2 bxc4 14.Bxc4 Qb8 15.b4 Qb6 16.Be3 d5 17.exd6 cxd6 18.d5 Qb7 19.dxc6 Qxc6 20.b5 axb5 21.Bxb5 Rxa3 22.Rxa3 d5 23.Ra8+ Kd7 24.Bxc6+ Nxc6 25.Bc5 Be7 26.Rxh8 Bxc5 27.Qa6 Bxf2+ 28.Kxf2 f5 29.Qb7+ Kd6 30.Rc8 d4 31.Qxc6+ Ke7 32.Re8+ Kf7 33.Qxe6# {1-0}
There is an old guy at my chess club who plays just like the Jonas bot. He starts off with dubious openings and then gradually complicates the position until I make a blunder and then he goes on to win.
The same thing happens to me with the Jonas bot. I have beaten all of the other bots up to Arthur, what kind of things do I need to do to get over this next hurdle?
Please don't just tell me not to blunder, as that's not very helpful. What I am hoping for is someone to say "I struggled with that as well and then I studied this and that and then it was easier.'