App Store Toolbar Missing - Macbook PRO Retina

Ever since I installed High Sierra 10.13.3 my Macbook PRO 15in Retina Mid 2015 (i7-2.8Ghz + 16GB + 1TB) has been lagging and running really slow! but this another issue or maybe it's connected.

My issue that I want to solve here is the App store has no toolbar at the top. It makes it almost impossible to use the store and makes the experience of using the appstore a terrible one!

I downloaded a new copy of high sierra and installed that on top of the current version. This did not fix the issue. I really don't want to do a complete FRESH OS install because I have a 1TB hard drive and it will take me a long time to go through and copy out all my files I want to keep.

Also, I thought an option might be to download a copy of Yosemite and install that, but without a toolbar I can't go to purchased in the app store to download a copy of Yosemite.

Any suggestions would be appreciated, I have a feeling the fact that the laptop is lagging and this weird issue with the app store are related. Perhaps the updates on updates of OS have left relics of old OS parts that don't interact well.

Thanks,

(image supplied showing how the toolbar is GONE!!! + my macbook retina specs - were top of the line choices in 2015)