I have a 'dumb solid' imported that import diagnostics does not recognise the features of. I need to make the outer indents 3mm in width and make the top diagonal edge go an extra 10 mm as the picture roughly shows.

I am having trouble doing either of these due to the complex nature of the shapes and the fillets

I have uploaded a file similar to the one I am editing and only half of it as I am trying to learn how to do this not simply just wanting it done.

Any help is much appreciated.

Thanks,

Harry, (student)