I’ve been trying to manual on and off for quite some time. I can’t get the front tire to stay up for more than a second. I can wheelie for a few seconds but I’m not great at it. I believe geometry and the weight of your bike have a lot to do with manualing. The youtube videos are deceiving because some people make it look like they can lift the front end up at will. With the average bikes being around 28-30lbs it’s not that easy. I’ve tried doing manuals on flat ground going up and downhill and everything in between. I just don’t care enough about it to make it a priority. If you find the secret to them let me know.