speech parts in Prepositional case are always preceded by preposition, which is what the case is named after

to think about is думать о/про so as a result you have думать о тебе where тебе is ты declined in the Prepositional case
I see. And are "о/про" interchangeable in those scenarios?

I got confused because I know that:

как тебе Лондон means "how is london for you"

But you don't say,

"как за тебе Лондон" you just say "как тебе Лондон"

I thought it's the same, but I guess it just doesn't work the same in the prepositional

насчёт in Hebrew would be 'be-noge'a le' or 'be-kesher el' so the difference is the same as between these prepositions and preposition 'al'
But you can also use "в связи" for those stuff, right?