If the loco in the first picture is what you are working with then my advice, which come from experience with one, is keep the body and throw the rest away.
The drive is that weak it could not pull the skin of a rice pudding and will fail under a heavy load which is what has happened to yours.
Look for a economical motor block and put that under it.
I put a USA trains block under mine and it worked fine, I later carved it up and used the parts as the front for my railcar, the other half is an old LGB coach.
Edit: If I remember correctly the guage is not correct for 45mm track either.
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