I don't mean to be a douche, but that's some of the worst soldering I have ever seen. Even the switches that currently work are going to start malfunctioning with that many dry solder joints. I can see legs that are probably not bonded at all to the solder outside of physical proximity.
Are you using good 60/40 solder? (I like Kester rosin core) Are you using any flux if your solder doesn't have a flux core? Any time the solder looks dry like that, try adding some flux and reflowing it. Only heat the pad and/or leg as long as you need for the solder to flow (if it doesn't want to flow, add flux). Try not to move any part of the joint while the solder is drying.
Nobody is good at it when they start, and cheap tools and bad solder don't help. Don't let this discourage you.
Here's a universal post I made on fixing lifted pads that can be applied to
most keyboards. It is the lazy/nuclear option. You don't need to figure out the matrix to do it. The only time it will not work is if trace continuity is dependent on the pad itself. In which case, you would need to figure out where that row or column leads and fix the break with a jumper. I don't think that's the case with this one.
If you do end up needing to figure out the matrix, you're going to need some really clear pictures.
suicidal_orange is really good at that stuff.