When I try to start the car the battery smokes.

I couldn't get it running.

I posted on youtube
or see attachments

 

It appears smoke is emanating from the junction of + battery main lead and battery + post

This is usually as a result of poor connectivity, you are electric arc welding as a means of cranking the starter motor

A few common faults, the main battery connector can be a loose fit on the post, ensure it is absolutely tight and cannot be twisted,
sometimes the slot needs to be relieved so the clamp will fully tighten on some battery posts, very annoying

The other fault is bi-metallic oxidisation, so remove cable and clean inside of clamp and terminal post with grit paper and wd40 till it is shiny

Ensuring all Earth terminals and other main cables and mount points are ok is a good idea

This should work

If it does not, how old is your battery, measure with multimeter should be over 12.2V

Do not ever hammer down on the battery posts, it can crack the soldered metal connectors

 

The OP may need some of this after repairs and maintenance are completed per your suggestions.