Looking for assistance on answering a few questions below. I had to create $5$ static web pages for an online business that sells office furniture. The static sites include $$Home$,$ About, Products, Login, and Contact$.....$

Which web pages should I secure using SSL$?$

Why should the selected pages be secured?

Which certificate authority should I suggest and why?

Which type of SSL$/$TLS should I recommend and why?

Are there any disadvantages of using SSL$/$TLS on all of the web pages?