Speed chess is always more difficult for players who are newer to chess because you must rely more on your known patterns and intuition of the game than calculation and evaluation determinations of positions. Because of this, you’ll generally blunder more or fall into opening or tactical traps more frequently. I recommend avoiding speed chess until you’ve gained more experience with chess, first because you’ll learn better chess habits using longer time controls and secondly because you’ll improve more quickly and likely be in more games in that process if you develop a good thought process. In fact initially I suggest Daily chess and basically avoid time controls while learning basics of chess fundamentals to help accelerate this process overall, or minimally a 15|10 or longer time control of a Live game format is desired to be played. Otherwise yes, speed chess will give you mixed results most likely and even more likely, could stunt your improvement, especially if you aren’t analyzing your mistakes and developing superficial gameplay (cheap opening tricks, surface level calculation and thought process of positions, ect). I recommend you try longer time controls for now and after awhile maybe revisit speed chess and see if you notice a difference. Have fun!
-Jordan
I've been playing some 5 min + 3 seconds chess lately and I'm wondering why it's more difficult than other formats? I've improved at 10 min chess and I figured they would be about the same time. With 5/5 chess my rating is stuck at less than 500 and 10 minute chess I can get it over 800.