I'm a decent Mario player but one thing that's driving me crazy is this stupid 1-2 jump you know that one that you have to do if you don't want to be hit by a koopa or a goomba. Does anyone have a solution I'm playing on a original nes but pal version I have watched every single one of yt tutorials. Please help.

try holding left for a little bit after you jump over the koopa. it makes that jump so much easier. im not too familiar with the pal version but from what ive played of it, it should be the same in this regard

If you're trying to do a short jump, I'd recommend essentially flicking the a button on your controller. For my controller grip I use my index finger to hold b and can flick my middle finger to get short jumps.

Another way is that before that Koopa and Goomba, there are 2 Koopas. Draw one of those two and hit it forward so it will draw the others for you and you move behind it.

What I personally use there is let go of B and slow down enough before jumping that you dont have to do a hard jump to clear the Koopa safely. It gives you enough time to do another jump over the Goombas with running speed after you land. It is slightly faster than the strat where you hit and follow the Koopa shell.