Present Perfect = Something started in the past but it still continues. We talk about actions that happened some time up to now.
He has never played the guitar.
Have you ever worked there?
Signal words: ever and never
IRREGULAR VERBS: have/has + 3rd word! (fly-flew-flown)
If Tim sees me, he’ll know that I’m not ill.
or Tim will know that I'm not ill if he sees me