If you want to get better at playing harmonics i recommend learning to play megadeth's tornado of soals even if you are not into them there is still some good harmonic parts that you can practice.As for solos try clicking on the easy section in the upper left hand corner there are a ton of really good exercizes in there that you can play and even improve on if you like.One of the best ways to get better at improviseing is SCALES play them all the time to and use them to come up with your own lines.I hope this helps even a little there are so many ways to learn everything its hard to pick where to go next.Search around on this site and you will find all kinds of great tips and tricks to play and most important of all have fun :)