I am new to Avast. Every time I run a scan it deletes my passwords how can I stop this
First I would suggest stop running the scans and what scan is it you are running ?
What passwords are being deleted ?
With a resident (on-access) antivirus scanner the need for on-demand scans is much depreciated. For the most part dormant/inert files are being scanned, the other active files are going to be scanned by the resident shields when they are activated.
Why have the scan in the first place? CRAP!