time management

I have played chess casually since I was a boy. my niece has shown me chess.com and I have been enjoying it thoroughly. my biggest issue seems to be time management so I've been practicing one opening over and over again to try to gain some time advantage at the beginning. my problem is that I have to strategize during middle and opening and it eats up my clock. Does anyone have any suggestions on middle game movesets or tactics I could study to save time in the middle and endgame. I've been hitting the lessons and puzzles hard and can solve them all pretty well, but some of the solutions take 45-60 seconds to solve which is fine for puzzle solving, but downright bad if I had to figure these scenarios out on the fly. I have started with Rapid as it has the fat 10 minute timer and I can get done with a game with 4-5 minutes left so I feel like I'm close to being able to play the five minute games effectively. any advice on stepping into that next threshold would be appreciated. Thanks.

My advice. If you are having time troubles on 10 minute games, play 15/10 instead. Playing blitz is probably a bad idea right now since you don't have the pattern recognition down. It's not going to help you improve.

You're around 400 elo. Around this elo range, most people blunder pieces left and right. So if you can avoid blundering and snatch up a blundered piece, your middle game plan should be trading down into an end game where you are at least a piece up. There's no advanced tactics you need to worry about right now. That's over complicating things and I don't think it will matter too much until you get near 1000 elo. Just try to play principled chess and do blunder checks before each move.

Rather than memorizing specific move sequences in the middlegame, focus on typical plans, pawn breaks, and piece placements that arise from your chosen openings. This way, you’ll recognize familiar patterns instantly rather than calculating everything from scratch.