well if starter spins with the key then the solenoid is good, The solenoid just "jumps" the heavy cables so wires don't burn up
So starter spins but engine doesnt turn over, first thing I would do is pull out the plugs and and pull fuse for ignition, try turning motor over if you can not hear air huffing from spark plug holes engine isnt turning over just the starter is turning
If engine has to much resistance to turn (like when it tries to start) it will kick the starter out of gear and just spin
I would pull the starter and check the teeth on it and then using jumper cables attach the positive to the starter lug nut (do not touch it to bare threads it can arc and mess up threads) and then touch the black clamp to starter body to ground it you do that 2 things should happen
1: the starter spins
2: the bendix will kick out the gear that engages with the fly wheel and spins
or 3: you dont have your foot on it good enough and it rolls around on the ground trying to pit bull your ass
https://www.youtube.com/watch?v=LYioIBeUedw
if starter spins but the gear does come out, take starter apart and clean it
what does it do now?
Does that sound as clear as mud
I just confused myself re-reading it