Hello Bigguy,

Doing a fast reading and understand the whole thing is not easy. It needs to take a great deal of time. If you want to read fastly, you have to practice reading everyday. The important thing is you start something that is appropriate for your level of English, not something too difficult.
Also, when we skim, we will understand the general idea of the text, not all the detail. So, it is very common that when you skim, you get only 60% to 80% of the information. Don't feel bad about it.

Greeny