The person is not accustomed to it yet as they need a few more years. So it's a change in progress, for which we use 'get'.

It's something that is STILL difficult, so he's not familiar with/accustomed to it yet. Also, grammatically, 'used to' does not fit as it comes after the verb 'to be'.

If a verb follows 'be/get used to', we use verb+ing.

There is no difficulty or problem anymore so it's not a change in progress. It's something s/he is familiar with/accustomed to already. We use the present as s/he is talking about being used to it now, not in the past.

This is an example of 'used to' for something that is a person is not becoming accustomed to, so it's still difficult or strange. This could perhaps be because they have not been doing it for long enough yet.

This person is discussing the process ('over time') of becoming accustomed to speaking French in the past, so it needs to be 'got'.

This is referring to the future.

The '-ing' form is used if we are wanting to place a verb after ' be/get used to'.

This isn't a process of change - it's a one off situation.

You can't use the present perfect with 'used to' - it has to go with the verb 'to be'. However, 'get' is the main verb and it conjugates for tenses.