Hi, my name is Neil, I'm an independent adviser and a Windows 10 user like you.
This is a hardware problem, but let me see if I can offer any help or advice.
First of all, is it a desktop system or a laptop?
If you're using a desktop keyboard, then you could try hoovering with a vacuum cleaner. Turn it over and give it a couple of knocks and turn it on it's ends and do the same thing. Try running the vacuum cleaner over the keys and pressing them up and down at the same time. It could have something stuck under the F key.
If this doesn't work, then buying a new keyboard would be the easiest option. They're pretty inexpensive.
If it's a laptop, then usually (do not try unless you're sure) you can pull the keys off the keyboard. They snap off and on. Try taking the F key off and seeing if there is something restricting the key being pressed. It could be something as simple as a hair!
There's not much else I can help you with really since it is a hardware issue. However, if it is a laptop and you're unsure about the keys, then send me the make and model number and I will check for you.