NEW CONTRACTS TOP TEAM

Hi Guys:

1st season: began with Manor
...
2nd season: still Manor, R&D 100%, leading Championship, 7 races to go, will finish champion very sure

In current 2nd season they did offer me to stay @ Manor.(offer after GB race) There were some other offers such like Renault, McLaren.
So I did sign for 3rd season to stay @ Manor because after all R&D most competitive team at the moment.

I was able to beat my rivals Hamilton, Rosberg, Ferrari, Wehrlein, etc.

Will I be able to get an offer from a Top Team end of this 2nd season ( after last race UAE ) ? Ferrari, Mercedes, Red Bull ?

Also, if I should receive an offer from a Top Team. Will I still be able to sign for 3rd season or is my accepted offer from Manor ( after GB race ) binding for 3rd season now ?

thanks for your expertise