xl is probably too big. The KTM is a basic bicycle. Nothing wrong with it, but it does seem run down so may need a lot of new parts. Give it time. A good bicycle should be the right size! The Schwinn does have a much nicer frame, which means less weight and more comfort. Not all steel is the same, there is a difference in quality.There is something appealing in that longer fork, maybe it's more comfortable.
I found a Schwinn Crosspoint for 50 euro, ruffly in the same shape. But the frame is Xl, and I am 175 cm height. Maybe it's too large frame for me?