You need to take it to a shop that does wheel alignments, it's beyond the scope of a home mechanic.
You can't fix it till you know what's wrong with it.
There is no way to change gear ratios.
Replace the instrument cluster.
It is not repairable, you should replace the instrument cluster.
These parts are only fixed by replacement.
There is no fixing a broken motor mount. Replace them with a new ones.
remove the battery terminals for a minimum of 10 minutes.
You would fix it by replacing the instrument cluster. The speedometer itself may not be faulty, it is more likely to be a problem with the speed sensor.
Check fuses If you are getting power to socket, but not through it ,replace socket
You would need to be more specific with your question. You are not providing enough information to supply a meaningful answer.
Have you checked the rear hatch glass ?? Open it and reclose it firmly.
The engines thermostat is probably stuck open or has been removed, so change the thermostat and this should fix your problem.