Sharpen foreground of VIDEO

I just shot a interview on video where the foreground that is the interviewee is out of focus and I tried to use video enhance AI to improve the sharpness but have not been able to see any improvement. I am wondering whether the fact that the background is in focus interferes and is stopping the program from sharpening the vision. Would a solution be to mask the background and which program would be the best to use to sharpen the video?

Davinci Resolve has features to correct focus which may be worth a look.

The free version is extremely powerful but has quite a steep learning curve for beginners;