If you have been in the UK for five years already, there are probably a few different options open to you in terms of staying indefinitely.
It is usually easier to secure a visa if you have been here for a long period of time already.
Have you checked out the Immigration section on the Gov.uk website? I would use this as a starting point to what possible visas could be available to you, but in terms of finding out how to get one, I would look elsewhere.
This website gives you a very narrow, to-the-letter explanation of things, and, in my opinion, can make things sound quite daunting and difficult.
You should find a licensed immigration adviser[here] to get an unbiased, realistic opinion about what your chances are, and know immigration law and loopholes inside and out.
Immigration advisers provide an excellent service to help you every step of the way the application process, which you may not want to pay for (it's pretty expensive), but before they take you on as a client, most will offer a free assessment session to go through your circumstances with you to let you know whether they believe they could help you or not.
This is what I did when applying for residency in New Zealand, and found the advice invaluable. I also saw 3 different advisers, to get a second (and third opinion). Good luck!
