[lamchob]

I second every comment on heavy lifting and do it myself on regular basis. But please, if you have never "lifted" before don't just waltz into a gym and start yanking on barbells. This can kill your back for good.

OP's Stronglift 5x5 is based on another program, "Starting Strength". Invest the money into the "Starting Strength" book by Mark Rippetoe. This book is "standart" in the powerlifting community and it's a treasure trove on body mechanics and "strength science". It will help you understand how to perform the basic barbell moves, based on body mechanics. For example, a lot of people struggle with mobility during squats. Don't push your depth with poor form, but ease into it, until you can go "ass to grass".

Edit: Record your lifts on a regular basis, to check your form. If you are unsure, /r/fitness provides form-checks.