I am staying in the Mitte quarter of Berlin, which I think is near a lot of sites. It is hard to evaluate tours. I am history buff and I want to take a Third Reich tour and a Potsdam tour that includes a tour inside Sans Souci.
Also as a senior age 65 I wonder if a bus tour vs. walking provides narrative along with stops at tour locations, but there don't seem to be many small group bus tours. I understand hop on hop off just has recorded narrative. I can afford to pay more for convenience and my knees, although I am not averse to walking.Some tours are only offered on one day and I am there from Saturday through Friday departure.

Also, since I will be on my own, are there good cafes or restaurants where I can watch street scene? Shows (variety or cabaret where lack of German language would not impact) and where I would not feel out of place attending solo? I am not looking for a single scene.

TTT,
Hoping your trip is not over, and that experts will reach out!

I'm a solo woman who dines out alone frequently, from casual eateries to Michelin 3-stars. I take my Kindle (not a device that shines light on my face) and relax and enjoy myself. No one cares, and if they do, too bad!

I don't know the tours you are considering, but I can say that Sanssouci (at least) is easy to visit on one's own -- and it's a delightful place.

Enjoy your trip!

There are still bus companies which offer sightseeing / HOHO tours with live commentaries in German and English.
Like this one: https://tempelhofer.myturboticket.com/
You can easily identify the buses, as all of them have that white livery with the German and UK flag and the word "Live" on the sides.
I don't think you need to book in advance, just ask your hotel reception for the nearest bus stop.

When you have good weather, you can also do sightseeing by boat on the river Spree (and beyond) from centrally located piers in Mitte (near the rebuilt city palace or the Radisson, you cannot miss them).

For variety shows, try either Wintergarten or Chamäleon.
Wintergarten usually has a certain music motto for their shows, and also offers pre-show a la carte dinners. Just keep in mind that the seating is not like in a theater or movie theater but with ordinary chairs around tables (so you can drink and eat while watching the show). So, it's not as comfortable as sitting in a comfy theater chair.
https://www.wintergarten-berlin.de/en/
https://chamaeleonberlin.com/en/tickets

The bigger shows are at much larger venues, like Friedrichstadtpalast.
https://www.palast.berlin/en/?noredirect=en_US

All of the above are suitable for international visitors who do not speak any German (including communicating with staff or when ordering drinks etc.)

In any case, I would check out the official TI website at visitberlin.com
So you know what's going on when you are around - as there are a lot of festivals and temporary exhibitions going on in summer.

For Sanssouci palace, I'd get timed tickets in advance as you can access the (small) palace with timed tickets only. If you just show up, you may still be able to get tickets for the same day. But often with a substantial waiting time until your time slot is due.

The OP didn't say anything about being afraid to dine alone or wondering what other people thought. She just asked about restaurants where she could people watch (to the street). This would be very common in Paris where there are so many streetside cafes. Other cities don't have them so much, although you can find them in Krakow and PRague, also.

SO that's the question, not about being afraid to eat alone. I don't know Berlin although I'm plannig a trip there and there don't seem to be many restaurants like that in Mitte, but maybe someone can answer as to that question.

I dine alone a lot and never read books or listen to them, I wouldn't enjoy a book that way and couldn't concentrate. People have their own preferences about reading books, I can't do it at a dinner table. I may read something, but it is likely either a local newspaper (especially at breakfast, in Paris the cafes have newspapers in them for clients to read), if I know the language. Otherwise, I take with me several copies of magazines I haven't had time to read that are small and I can easily tote around in a daybag or something. I like The Week for news articles but short items so you aren't reading a really long article, I love that weekly. Or a couple copies of the New Yorker which I never have time to catch up on. I also may buy a local magazine or read local brochure info for planning trips, stuff like that.

A number of outdoor and indoor spot s in the same
location.. Berlin is great.

Geesh, Christina, the OP did refer to "not feel out of place attending solo," and even if that sentence was about shows, why make a point of criticizing those of us who responded? You can offer your input without that.

Outside seating is very common in Berlin.
Not only larger terraces in front of restaurants or larger cafes, but almost every place has tables and chairs on the sidewalk.
I cannot remember seeing the inside of any such place last summer (which was really dry and hot).
For people watching there are many good places, e.g. Gendarmenmarkt, Hackescher Markt, around Schlesisches Tor subway station, in any cafe along Kastanienallee, around Marheineke market hall and along Bergmannstr... and, of course, also on Kurfürstendamm, the main boulevard of the Western city center.
Being solo is not an issue, regardless if you just want to sit down for a coffee at a cafe or a full dinner at any restaurant.