Hi Ann, I'm still learning, like you, but I'm familiar with this word. It has two meanings. First, it means once - not like "I ate once today" (so marra biljom3ah is incorrect, and jam3ah is Friday, not week), but more like how "once upon a time" is used: think "Once, I was eating". Also marrah can mean "a time, instance, or occurrence" - it is synonymous with "wa'it" which is much more common. And finally, in Levantine dialect, maraah - spelled differently in Arabic but pronounced identically, is the noun for "woman". Hope this helped.

And مرة بالزمانات marra bizemanat, which means ¨once upon a time¨.

Yes, both of the sentences you wrote are correct. مره بالجمعه translates to "once/one time a week" كل مره translates to "every time" كم مره؟ translates to "how many times..?" And جمعه can refer to the day Friday or the week as a whole, depending on the dialect :)

Like i will eating marra in the day

Yah correct mean it's once for everything