Is it fine to mail the Associate Editor in his personal email provided in his homepage?
I would avoid doing that, except as a last resort. The person is likely to be confused (best) or offended (bad). Try to work first through the journal itself. 

But also, it often takes quite a while for information about progress to filter through the system and it often takes quite a while for reviews themselves to be conducted. 

If it just "wanting to know" for informational purposes, I recommend patience. If it is "needing to know" for some other purpose then you can press it, but, again, go to personal accounts only as a last resort.

You could, of course, ask the journal itself how to contact the editor and whether it is appropriate for your needs.