How to change page and post title

There are options for setting permalinks according to your choice. Did you try that? Perhaps it will help you solve the problem.

Thanks for your answer. Unfortunately I am referring to posts and pages already published. I am worry that if I change their title and URL, the users that have already bookmarked them will get broken links.

You can change them and then create a rewrite rule in htaccess or use redirection plugin

Thanks for your answers.

I have one plugin, Simple 301 Redirects, that does that. It means redirecting every single post and page, right?

I read a post that said that it could be easier, but I thought of asking in case it was not THAT easy. This is the post: https://suiteminute.com/avoid-broken-links-when-you-change-the-title-of-a-blog-post-wordpress/

Another option would be to change only the title, not the URL. Do you see any SEO, broken link, problem with that?

There is a redirect plugin that is url specific. Should not impact on seo. From what I have read pretty permalinks are an seo winner>
Best of luck with it.

Thanks for your help