Change Wordpress post type names without affecting the content or pages fix menu

I have a Wordpress website (see attached doc) with post types which I want to change the name of, so the links are relevant to what I am doing. Post type name changes are: Lessons - change to - medical-skin-tattoo-treatments Catalog - change to - medical-skin-tattoo-casestudies I need all the link of the existing Lessons and Catalogs to be changed e.g. /lessons/postname to /medical-skin-tattoo-treatments/postname without changing any page layouts/designs, content etc. All must remain exactly the same other than the link names. I have tried changing the permalinks but this isn't working. Tried doing a find and replace on the whole theme file but this causes further issues. I then want to make sure that these newly renamed post types are available to add to the menu, as at the moment they are missing for some reason. I need to be easily then able to create new items under each post type and this will show on the relevant sections and I can add to menu. So it is changing the names of post types moving forward and adjusting existing items now. Also as part of this project, I want you to detail the exact instructions on how to did it - this is part of the project so make sure you are able to write out each step by step on what you did to change this, including what pages you edited and what you did in wp-admin. Important! This is a quick easy job for someone who knows Wordpress. No timewaster and no one who is going to mess up my website even more due to incompetency please - experts only!