Adlago

If your host offers it, choose Redis.

Now for your site
www.jonado.net
I see this

You log in to this site in your Client area
Download latest version
Extract files
Log in ftp
Uploads all files
Open browser
Start ..../admin/upgrade

Have you tried this:
In a list of tables in your database, select this table.
Scroll to the bottom, under a list of tables in the drop-down menu With selected, select Repair table.

Only one simple rule in code is missing.
Or - now a code that defines this blue bar is
@media screen and (max-width: 979px) ( #elMobileNav { background: rgb( var(--theme-main_nav) ); color: rgb( var(--theme-main_nav_font) ); position: relative; display: flex; justify-content: flex-end; align-items: center; list-style: none; margin: 0; padding: 0;} }
and as it is changed by adding height, it should be
@media screen and (max-width: 979px){ #elMobileNav { background: rgb( var(--theme-main_nav) ); color: rgb( var(--theme-main_nav_font) ); position: relative; display: flex; justify-content: flex-end; align-items: center; list-style: none; margin: 0; padding: 0; height: 50px;} }  
Or just add in Custom css
@media screen and (max-width: 979px){ #elMobileNav {height: 50px;} }  

Open Search Engine Optimization in your ACP.
In the Meta tag section, click "Launch Live Meta Tag Editor"
Your home page site will open and on the right you will see this editor. On the site, select the APP you want, including a blog, and on the right you'll be able to change anything you want, including the title of the APP.
Of course, don't forget to save changes before closing the editor

Restore this.
But the lack of many pages in your site, is some kind of lack in the database, in my opinion. Look for a backup option

Open Search Engine Optimization/Meta tags
At the top right, click the button Launch Live Meta tag Editor
You will see on the right of your home page a feature column Live Meta tag Editor and at the top field you can edit the page title

This mod is applied to "regular sites". In this case, look for other forms of optimization, but remove this mod.

Try creating a copy of your theme, then try downloading a copy theme.

Use the ACP tool and clear the cache.
Your JS is currently being loaded with outdated cache and is therefore not working.

Open: loginPopupForm template (core_front_global)
Find
<input type="checkbox" name="remember_me" id="remember_me_checkbox" value="1" checked aria-checked="true"> and replace
<input type="checkbox" name="remember_me" id="remember_me_checkbox" value="1"> For me work good

In your theme, you should create a template. For example

 
Open this template core_global_analysis/preload_css, and add this code
{{foreach array_unique( \IPS\Output::i()->cssFiles, SORT_STRING ) as $file}} <link rel='preload' href='{expression="\IPS\Http\Url::external( $file )->setQueryString( 'v', \IPS\Theme::i()->cssCacheBustKey() )"}' as="style"> {{endforeach}} and Save.
Open your global template, and add before
{template="includeMeta" app="core" group="global" location="global" params=""} This
{template="preload_css" app="core" group="analysis" location="global" params=""}