Make some changes in my website

Hello there, I have an e-commerce website which is pretty awesome. I've just made a webview app for my website and there are some easy and quick changes to the template I need to complete it. 1.- I need to add an Age-Verification PopUp (already had one before but changed my theme) 2.- I need to add a Button that sends directly to Whatsapp Business Chat 3.- I need to fix the code that makes that WebView doesn't send the forms of authentication when loging/registering (but that works fine at Safari) 4.- I need to add a "Back" button in some parts of the template 5.- I need to make my "Go to top" button a floating button in all the website. Please, just serious bids. Its a quick work so I won't be taking bids that doesn't read all my description.