How can I best enjoy an audiobook in English when I have difficulty in understanding the English speech?

Well, I’m an English speaker and I sometimes have difficulty with speech for some readers. I will usually return the book for credit. In terms of how to best understand it the only thing I can suggest is to slow the narration down in the app.

Try one of these:

Translate All – Voice and Text Translator App
https://play.google.com/store/apps/details?id=translate.all.lang

Language Translator Earbuds
https://www.amazon.com/Timekettle-M2-Language-Translator-Earbuds/dp/B08GLY854H/ref=mp_s_a_1_6?keywords=voice+translator&qid=1649194997&sr=8-6

Or listen with an English speaker beside you, if possible. One of your friends perhaps.

Try slowing down the audio. Listen to the first pages several times until you understand (almost) every word. Recognize that you’re doing something slightly above your comfort level and it’s probably “working” even if you miss many words later in the story – as long as you can follow along and get the gist, you’re learning.

If it’s still too difficult, practice listening to English first: it can work really well to listen to an audio book while reading the original. ESL podcasts are great, too.

Have a text copy of the book as you’re listening and follow along by reading it.

You also might want to watch some movies in English to help train your ear. If you miss something, replay that section with the English subtitles on. I suspect after a few films, your ear will be much better honed to picking up the meaning.

The more you listen to English, the easier it will be to understand.

Maybe consider it a lesson learned and stick to audio books that you can get a printed version of, to follow along as @janbb suggests.

Does the Audible app have a setting to slow the speech?

Your written English is excellent, by the way. I never noticed that it may not be your first language.