I can climb trees

Let’s pretend for a moment that one of my skills is tree climbing.  Therefore I have the ability to climb trees  (or I am able to climb trees).  But in conversation it is much easier to use the word ‘can’ in sentences to describe abilities.  Try to use ‘I can’ do something rather than ‘I have the ability to’ do something and the sentence becomes much easier.

I can climb trees.    (present tense)
When I was younger I could climb trees.     (past tense)

You can also use ‘can’ and ‘could’ when the context is a possibility e.g.

Is it possible for you to come to a party tomorrow?     – just say ‘ Can you come to a party tomorrow?‘
Yesterday, there was the possibility for us to meet for lunch.    –  easier to say ‘We could have met for lunch yesterday‘

Sometimes though, the use of ”to be able to’ or ‘to be possible to’  might help clarify the situation better so you can still use them.  Either way, you will be understood.  Here are a few more examples for you to correct yourselves if you want:-

Is it possible for me to come and stay with you to learn more English?
Are you able to to offer discounts if I stay longer?
At the moment, because of the pandemic I am not able to come and visit you, but this may be possible in the future.