Avast Free Antivirus featues issue

[REDACTED]

I am facing 3 different issues in Avast Free Antivirus v18.2.2328 (build 18.2.3827.306), Virus Definition v180319-0, Number of Definitions: 43.65.115 in my laptop Windows 7 Ultimate 64 bit.
1. Avast Free Antivirus recently detected a threat in "avast cleaner log" file, this threat is detected in "full scan" operation(set as sheduling scan). So I stopped scan manually, restarted my laptop, connected to internet and performed "smart scan", smart scan operation does not detected any threat, then I performed "full scan" operation manually, this threat is again detected.
2. I am facing problem in specific file scan, sometimes this scan is not work, sometimes it is not immediately start, unless I started Avast antivirus(startup is enabled by default). Specific file scan means right click scan in windows explorer.
3. Scanning speed is very slow, sometimes scan completed, but still showing scanning operation, because may be a problem related from UI.
Unfortunately there is no option available to upload screenshot for better understand, because insert option(provided in this forum) is not working.

[bob3160]

Repair Avast:
Control Panel> Program and Features (Add/remove program)>Select Avast> Select Repair. Reboot when completed
https://www.avast.com/faq.php?article=AVKB204
If Repair doesn't fix the problem, try the following:
Clean Install of Avast:
https://goo.gl/4Ptzkf
You can attach a screenshot using Attachments and other options

[REDACTED]

Thank you so much for provide instructions, this is a screenshot of my 1st issue.

[Asyn]

You can report a suspected FP (File/Website) here: https://www.avast.com/false-positive-file-form.php