Android Launcher Loading Problem I'm desperate, otherwise I wouldn't post this long type of post on this forum, cause whenever I have a problem, I just search it on Google and 99% of cases I find the solution, but this time, I'm helpless. I would really appreciate if someone has a solution to my problem,

I have a Infocus M2. It is an awesome phone, I'm really satisfied with it. I have it for 1 year now and I have never had a problem, everything worked perfectly (and is still working), but for 7 days something keeps popping up: it doesn't matter if I'm in a game, or on the internet or am I doing something on the phone, a black screen with text "Location service" and after that a white screen appears with a little text "Launcher loading..." and a circle that is loading, and I have no idea what is that. I can't do anything, I just have to wait like 1 minute for it to disappear. After that a new app automatically start installing from Google play store. 

All this problem started when I install a free app "Task bucks" from Google play store. and this app automatically install a app "Key Chain" After that I just loose control over my phone. Whenever it connects to internet it start downloading apps like DU Speed, Battery Doctor and some those apps automatically install that I uninstalled 1 month ago etc. It's really frustrating. Also, this happens, like one time in 1 hours. I really hate it.

I have to mention a thing:


Some times After the white screen disappears, Google App Store opens, at a shopping app called "Ali Express" (like it wants to install it or something), I had it installed only one time, but I uninstalled it 6 months ago.
Key Chain does not remove by restore factory setting. that is automatically installed from Task bucks

Note: I know one Key Chain is default app but my phone has 3 key chain


I have Attempts following steps to solve my problem:


Restore factory setting and deleted all third party apps 2 times but problem is still.
Run up to 4 antivirus apps but no luck
Change google account password
Boot my phone in safe mode and clear cache, clear defaults of some apps like: launcher, key chain, location service etc. and Reset app preferrnces. 


I'm sorry for the large post, but I wanted to be as specific as possible. Thanks in advance.
If your phone is rooted you can use Stubborn Trojan Killer.