I would suggest checking the coolant, and making sure it is bled properly - which can be a rather involved process to do it correctly.

The basics

Cold engine
- check that coolant level is correct
- Ignition on but engine not running
- set heter temp settings to max
- set fan manual to one of the lower speeds
- start engine and within 30 seconds rev it 3-4 times up to 3000rpm
- shut off engine before end of 30 seconds (before it starts to heat)
- reset climate to normal settings
- recheck coolant and top up if necessary.

Hot engine
- take car for a run to get up to operating temp
- using caution - slowly open the bleed valve (steam and bubbles may come out)
- close as soon as you see liquid coolant without excessive bubbles.
- do not overtighten this as they are plastic threads. Just snug till it seals fully.
- after engine cools check the coolant level again and top up if necessary.

Check coolant level every few days for a few weeks and top up again if required
- repeat the Hot engine bleed process again.

If coolant keeps droping after 2-3 top ups have the system pressure tested.

If you are still getting over temps have it analysed by a dealer. The temp is controlled by the engine computer so there may be another fault.

Cheers
Jim Cash