S7 wifi dropping in and out?

R11

My S7 is over 2 years old now. Recently,it has developed a wifi problem. It connects to home wifi no problem but some pages take ages to load while others load straight away. Same on Facebook,some pictures/videos load while others dont. So it seems to be dropping in and out every few seconds/minutes(but wifi symbol at top is fine). A friend in work had a similar problem with their S5 last year,went to a store,they said that the phone is near the end of its life when that happens.......I've reset settings,forget network etc but still the problem is there. Any advice??