Hi,
I'd like to hear something from Joomla51.

you have to install the components/extensions separately

Thank you for your reply.

I tried this. I am no programmer however.

Because I cannot change the limitation of upload files (support by my web host is minimal on this), I could not upload any file.
I tried by transferring the whole package by FTP to the public_html/tmp directory of my website. I tried installation then with the unzipped package and the alternative leaving the whole package unzipped because the former did't work.

It does not find the install file j51_london_j4.zip (according the instructions: "install file for your template from the download that you have just unzipped. You will find this located in the Joomla! [JoomlaVersion] Install Files folder, titled j51_[TemplateName].zip.". Each time I get error messages like "JInstaller: :Install: cannot find XML installation file", and "Path does not have valid package" and "Could not find 'manifestfile' (translated).)

Whatever path I try no install file is found.

I also wonder why you have to unzip everything if the install file is supposed to be a zip file.

I upgraded Joomla to version 5.2.2 and PHP to version 8.1. This caused all problems with my existing website that couldn't be published anymore. Because also of phishing attacks I decided to rebuild the website.

I would appreciate some further help.

Unzip your template download. it gives you 3 maps:
demo installer
joomla4 install files
template extras

in the map joomla4 install files you will find j51_londonj4.zip and a lot op mod zips. Log into your joomla admin and install your j51londonj4.zip and the mods.
your schermafbeelding indicates that you installed the template successfully.

Thank you for your help. I managed now.
Cheers