1. You don't need to translate the word "sui" in the sentence. It is easy to take "fitness centers appear all over the world" as a noun phrase and take it as the subject. The previous composite structures are all wrong. It is also possible to translate it into a compound structure, but the subject should be added later.
The emergence of fitness centers around the world has brought us great convenience.
2. "I work eight hours or more a day" can be used as the subject. "At the same time" is redundant, get rid of it. The latter "this situation" refers to the former situation, which obviously does not need translation. The time of this sentence is unclear. Is it expected to happen or has it happened? I processed it into the present perfect continuous tense, indicating that it has been five days and may continue.
Working eight hours or more a day has lasted for five days.
~ ~ English teachers ~ ~