My WiFi Not working properly On Mac Os High Sierra

Hi, Everyone how are you? I hope all is going Well, guys am facing the problem with my wifi. My wifi is not working properly, and Sometimes my wifi is connected to the internet but show slow browsing. And sometimes it's not connected to the internet and show msg for diagnosis wifi etc., I just restart my MacBook and then, work fine. From last 3 days, i have speed issue with my Macbook. I have to check my internet speed on my Windows PC, Where speed is fine but when I use internet on my Mac then, speed is too much slow. I mean slow browsing. And also if I disconnect the internet and turn off wifi and then, turn on wifi then, did not connect to the internet until I restart my Macbook. Guys tell me what I can do my system specification is given below:

Note: Am using CleanMymac for cleaning Cach and browser and system history.

Model Name: MacBook Pro Mid 2015

Model Identifier: MacBookPro11,4

Processor Name: Intel Core i7

Processor Speed: 2.2 GHz

Number of Processors: 1

Total Number of Cores: 4

L2 Cache (per Core): 256 KB

L3 Cache: 6 MB

Memory: 16 GB

Operating System: MacOs High Sierra v10.13.1