Newbie Help with new theme

The theme I purchased has a fatal error message so my hosts deactivated my theme and suggested that I contact my theme developer (I’ve been using the theme for 4 months now!) so I am using GreenLeaf Free Theme for WP temporarily but as I am new to all of this I am looking for a bit of help. On my front page I showed certain blog categories under different headings but now all I see is the hmtl code. Can anyone suggest how I can fix this? https://www.yorkshiretots.com I have a feeling it’s simple I just don’t know how.

Also, where my contact forms were is also just html like here https://yorkshiretots.com/new-group-form/ Are there any suggestions for this as well?

Thanks so much! I have spent so much time on my original theme I am a bit sick about having lost it.