Hi team!
Recently bought an old house needing lots of tlc.
The front external door has had a dodgy home job done whilst changing locks and filling in the gaps left. I'm thinking I will just replace the door for ease as it is standard size, but I'm not sure how best to go about repairing the timber frame. It looks like it's just been done with spak and left?
Should I chip this all out and replace with builders bog? Or is there another process entirely? Otherwise do I need to look at replacing part of the frame and is that something I could do myself?

Biggest thanks in advance!