Hestia And Frontier Post Issue

I have been using Hestia, and it has been a great theme, but I just recently realised that the plugin Frontier Post has functioning issues with it. If my posts portion is opened on frontend on a mobile, the form exceeds the margins.

I have seen similar problems with many other themes also, they exceed the margins on phone. Please help me with a solution. I tried going throigh frontier post pages, and tried increasing page size but it did not help.

The page I need help with: [log in to see the link]