If I change the turbo for focus st and swap a bigger one, do I need any other modification?

Basacly If i change my turbo in my ford focus st 2013 and put a bigger one from aftermarket, will I need to do amy other modification or just the turbo will be fine? If so will my engine heat up more or get damage or turbo or Ill be fine?

Depends how big the new turbo is. You may need a bigger intercooler if you have one. Fuel injectors might have to be changed. Exhaust or intake manifolds might be a restriction. New clutch. Depends how crazy you went.

Bigger turbo will be of no advantage and just waste money. Fix the one you have and get the car dyno tuned to get more power

Sure?

Probably:
Intake/exhaust modification.
Fuel injection modification.
Then will need to get a custom tuner/programmer and have it dyno tuned.

Then if you get into bigger power numbers:

Transmission.
Clutch.
Forged internals.
Etc.

Too much boost can blow up the engine.

You may need to alter the chip in the EMS