Hi I can enter my GMAIL account but there is a problem that I can not open my gmail the username & password are correct but a few weeks before one of my friends suggest me to mark Don't always use https in B rowser connection after that my gmail could not be opened. With great thanks & best regards .
F.Mohajerani gmail address: >Removed<

Have you tried un-checking the "Don't always use https..." setting?

There are only two reasons I can think of that your friend suggested turning off https:

Encryption slows your connection down
Years ago, the extra processing required to encrypt an http connection (making it https) did add a significant burden to the computer. However, today's processors are so fast this is no longer an issue. You are more secure using https!
Your friend wants to spy on you
Without the https connection, anyone on your network can sniff the data packets and read your emails, password, etc. Let's hope your friend is a true friend and not doing this, but anyone else could still be monitoring your emails.

Hope this helps,
WallyH