Does mitch lose control of the senate if democrats win the majority by winning Georgia? Or he will be leader despite dems having majority?

if the Dems win both Senate seats in Georgia then they will hold control in the Senate, since this would put the Senate at a 50/50 split and the tie breaker would be the Vice Presicent, which is Kamala Harris, a Democrat, The leader of the Senate (Majority Leader) will be whoever the Senate votes to be the leader, since the Senate will be controlled by Democrats is will almost certainly be a Democrat, more than likely it will be Chuck Schumer, since he has been the Minority Leader for some time 

If Democrats win both of the Georgia run off elections then they will control the Senate.  (technically it will be a 50-50 tie, but since ties are broken by the Vice President, and that will be Kamala Harris come January 20th, Democrats will have effective control).  The leadership of the Senate will pass into Democratic hands, presumably making Chuck Schumer the Majority Leader. 

The majority picks the leader. Fun fact, the best the Democrats can do is 48 seats, in the unlikely event that 1 or both of the independents sided with Republicans Mitch could keep the leadership position. If the independents side with Democrats as expected, VP elect Harris would be the deciding vote.

The majority party in the Senate chooses the majority leader. I don't think it would be Schumer, he is behind several other Democrats in seniority. Patrick Leahy tops the list. McConnell would probably move into minority leader position.

He would lose the Senate leader chair.  He would remain Kentucky senator nothing else.

Yes; Chuck Schumer