The martian maybe. Maybe even all the books by Andy Weir

I'd say anything by Asimov. He had a clear, simple style that makes it the perfect author for the no native English reader.

Not audio, but public domain... Little Fuzzy. It's a first contact story between humans and aliens who may or may not be sentient.

https://www.gutenberg.org/ebooks/18137

It's just a joy to read.

Anything by Andy Weir, he's basically juvenile fiction with really good ideas and research

The Expanse series by James S A Corey (also made into an excellent TV show). All the books are a very quick read, the pacing is fast but totally comprehensive. If you can get through medical texts and academic papers, these books will be no problem.

I really like the Pirx the Pilot series by Stanislaw Lem; ironically translated into English from Polish.

Try the Vorkosigan Saga by Lois McMaster Bujold. The English is outstandingly well written, but not particularly difficult. Outside of a few basic weapons and ship types, most of the jargon is military or biological, and pretty well explained.

The audiobooks are extremely well narrated with distinct, entering voices.

There's also, like, a million of them.

All available for free on hoopla.

Edit: I just read the rest of your post about real scientific concepts and struggling with narrative elements. Try it anyway! It's free and wonderful.

I don’t think simple plots and characters are connected with easy to understand language.

I think you should get a kindle so you can look up words on the fly, and then read good sci fi.

To that end, I recommend The Expanse series, starting with Leviathan Rising.

Delta V by Daniel Suarez is about asteroid mining in the near future.

Old time writer Poul Anderson has dozens of alien races and space merchants. "The War Of The Wing Men."

Robert A. Heinlein wrote a lot of YA novels that still hold up as stories. Obviously, there are going to be a lot of details he missed, but "Between Planets" is a good adventure story and "Tunnel In the Sky" is the original version of The Hunger Games.

What about something from A. C. Clarke?

You might like "the old man's war" series by John Scalzi. Basically aliens came to earth gave us technology and we created an earth defense army in space to fight the other aliens, but to join the army you must be 70 years old.

Another good series is expeditionary force. Aliens attack earth and one guy takes the fight to the aliens and with the help of a sentient super fast intelligent Ai captains a spaceship fighting aliens. This one is good but after the first few books the story beats and jokes start to repeat. The author should of stopped in my opinion around book 5 but he kept going with the same stories.

A bit unconventional, but I recommend Slaughterhouse-Five by Kurt Vonnegut. It's a thematically complex book, but not a difficult one to read or listen to, or to even follow. I listened to it in audiobook format, and it instantly became my favourite book ever.

Greg Egan's book "Schild's Ladder" is hard sci fi but digestible language. Some of his other books are more technical but this one is more straight-forward.

Perihelion Summer is another good one by the same author. Not as far out.

"Real scientific" Is Hitchikers real life yet? I can't speak for the other books in the series but Red Mars kept my dyslexic attention throughout even though it's pretty long, if that's a good analogy.

Not really based on scientific concepts, but The Breach by Patrick Lee is a sci-fi action thriller and very easy to follow as an audiobook

I'd recommend Jack Campbell's lost fleet series! Good characters, engaging story.

Xelie Sequence if you feel like scrambling your brain with some absolute hard sci-fi shenanigans

I recommend reading a book/series you already read in your own language. Then with context you can infer a lot of words which allows you to read quicker. It's not as exciting since you know the plot but can be nostalgic to read one of your favorites.

Flatland and Sphereland