Change the Title Tag from h2 to h1

Hello,
I have 2 probs:

1. I have a coustom template and the post titles are automaticly set as h2. I would like to have them as h1. I tried some h1 hacks found on the web, like this one: https://www.getwpress.com/seo/h1-hack-for-wordpress-pages/ but it didn’t work….

2. The post titles are automaticly the titles in html code (<title>Post Title </title>). I would like to be able to define the html titles. How to do it?

Thanks for your help!