I'm guessing that the code here is not literal but altered for expressing their content? It helps if you use "example.com" which cannot be owned and was made for the purpose of examples. ;)

<link rel="alternate" hreflang="de" href="https://site.example.com/title-of-the-page" /> appears to be fine, but should only be found on the English version of the page to alert bots that an alternate language page exists.

I would drop the nofollow part, you want the bot to take a look so they can evaluate it and index it. With nofollow, they can't.

Google offers their official instructions here: [developers.google.com...] and they include ideas and how-to for dealing with sitemaps for multi-language versions.

Thank you, @not2easy. I will try to use 'example.com'.

should only be found on the English version of the page to alert bots that an alternate language page exists.

As far as I know, the so-called 'self-referencing' is mandatory or optional, and I decided to leave it:

* [developers.google.com...] (the resource you link)
"Each language version must list itself as well as all other language versions."

* [semrush.com...]
"It might not be obvious, but you need to include a self-referencing hreflang tag for each page. In other words, every page needs to not only reference its alternative versions, but also itself."

* [ahrefs.com...]
"Self-referencing hreflang tags are included in the guidelines. But they’re really more like a best practice and not actually required."

* [screamingfrog.co.uk...]
"It was previously a requirement to have a self-referencing hreflang, but Google has updated their guidelines to say this is optional."

I would drop the nofollow part, you want the bot to take a look so they can evaluate it and index it. With nofollow, they can't.

Wouldn't the link harm the ranking of the text "Title of the page"? I mean, if I do not use 'nofollow' I would improve the ranking for "In English" text, right?

Wouldn't the link harm the ranking of the text "Title of the page"?

If you mean it could help or boost the text's importance - yes it could. It would be better if it were a complete phrase, as in

View this page <a href="https://en.site.example.com/title-of-the-page">In English</a> 

The "title-of-the-page" is not the important element in the hreflang= meta link, it is smply the name of the same page in English (or German) it is not visible to users so it doesn't matter hugely what the name is - that only matters on the target page. The title of the page should preferably be in the language of the page it links to, I mean, that is what you want indexed. If all the pages have only English titles, that does not indicate a well done translation. Think of it as "what would benefit a person who does not speak English" or "what would benefit a person who does not speak German" for the titles and descriptions of the alternate language pages. That is what they would see in a search result.

I apologize for using old notes, that is the reason I wanted to include the information Google currently offers. I do not personally manage any multi-language sites.

The title of the page should preferably be in the language of the page it links to, I mean, that is what you want indexed.

They are commercial names. The beginning of each title is the same one in English and in German, for the same item. I add just different words in English/German, at the end of the title.
- "Acme Pro", photos
- "Acme Pro", Bilder

That would be just right.