Thanks,
I have already a fresh copy of all my old AIS versions and avastclear (SfxInst v.10.3.2225.1172) , downloaded here and nowhere else ... instructions followed exactly.
Never others different antivirus (and firewall) program installed , I'm a 10 year (at least) avast IS user.
Other security programs I use : Malwarebytes , adwcleaner , JRT .
Except webshield (seems to work anywhere in statistics) , I can't noticed any troubles with my system (no slowness , no infected files , no blue screen ,no error messages to take care).
For language issue after repair, it's ok now , I install english language too , the french UI is ok now.
However , during repair or during web shield installer (tried to remove only this with control panel) , the file "KB970158_x86.exe\quiet" wait behind 1 minute , I don't know if it's normal (net.framefork file ?)