i know how to make biogas and also how to remove some elements like moisture and CO2, but now am stuck how i can make it methanol

 

I really hope this is some homework exercise that you do for highschool. Frankly, if you did not learn this in university, then I think the chance is very small that you will be able to design and operate such a process, but my biggest concern if you even try it would be safety.

 

The most common process is achieved in two steps: steam reforming and methanol synthesis. There is plenty of information, and just googling for [methane methanol reformer] got me a lot of hits already. This one shows a nice process flow sheet on page 4. These processes are very large, because they are just not economical at small scale.