Howdy 23286331 ,
I’m in this business since 1994 (then many companies had no client server archtctr but framewr) when mostly R/2 was still around..
You say You’re mechanical engineer – that doesn’t matter what are you originally as i met so many excellent colleagues who were originally matematicians, physicists, teachers, soldiers, webadmins ,or even bookstore managers .. So from this point of view You don’t have to worry whether you would be able to handle the assorted logic and processes of the SAP systems ..
Well however back to Your question: for Your case I’d strongly recomend You to start with PP and after some months to start to look also into APO/SNP just to have got an attractive combination in portfolio . MM is also very good to know for a newbie however by all due respect nowadays you’d be still able to catch that knowledge along while progressing mainly in PP… This is my advise.. However everybody sees this individually. It depends what you want to become later on..Do yopu want to be a consultant or just superuser on permanent job, or just common user…
Anyways widshing You the best and might be within two years it’d be You yourself contributing with some sneaky tips on all those (today there is so many of’em around already) SAP forums around the world