I have opened the toilet lid and the water appears to be leaking from the end of one of the parts, do not know what it is called sorry. Is their anyway I can upload a picture for you as this may be better? Thanks

Hi little feet and welcome, check here. Good luck

https://www.askmehelpdesk.com/plumbing/how-fix-toilet-has-hissing-sound-slow-refill-510760.html

This might help

Which ballcock is yours? Back to you, Tom