Get yourself a copy of the Lawn Expert, or borrow it from the library. Last updated 1997, so probably any commercial products mentioned might no longer exist, but all the care routines, weed recognition, how to recognise and deal with different problems are all in there. Its everything you ever wanted to know about lawns, from laying new turf to renovating an old lawn. This copy's only a penny, with under £3 postage

https://www.amazon.co.uk/Lawn-Expert-Dr-D-Hessayon/dp/0903505487