Windows have published a date when they will stop supporting 7 but its a few years away. Backing up bookmarks is easy and should always be done along with personal stuff before any significant upgrade. If you decide to do it we can send you a walkthrough.
You do NOT have to upgrade to Windows 10. Windows 7 is a perfectly good operating system and will be supported by Microsoft for many years yet. I have just bought a new computer with Windows 7, quite deliberately. With previous updates of Windows I've lost software and hardware that wasn't supported by the new system, so I've no plans to upgrade.
There are a number of programs that block Windows 10 from downloading such as GWX Control Panel but you will have to byte the bullet in the nex 4 years if you haven't replaced your current PC by then