I have been watching a controversial show sincefor a few years ago.

I discovered it while watching TV, it was broadcast in a channel called Discovery Home & Health.

Its name is "90 dDay fFiancé"," I loved it.

I can't watching it while I'm doing another activity.

I need to put/give my entire attention to understand the whole gossip hahahha.

A Dramatic and GossipReality Show

"Gossip" doesn't work as an adjective. But if you want to use it, you could use this alternative: A Dramatic Show With a Lot of Gossip
In general, it's common for reality shows to have a lot of gossip - so this would already be implied.

I have been watching a controversial show since afor few years ago.

I have been X for # years => you are describing an ongoing habit and when you started
I did X # years ago => you are describing an activity you did at a certain time in the past, and it is implied you no longer do this activity

Your original sentence is combining these structures, but they mean different things

I discovered it when I was watching TV, it was broadcast ion a channel called Discovery Home & Health.

We say shows are "on" TV or "on" a channel

It's name iscalled "90 dDay fFiancé"," and I loved it.

You are referring to the show by its name, so it needs to be capitalized

I started watching it in Spanish, but now, I'm studying by watching it in English.

A more natural alternative => I started watching it in Spanish, but now I'm watching it in English as part of my studying.

My husband told me that it isn't a good show for me because I'm learning bad words too, hahaha.

Learning bad words is important if you want to understand when natives speak ;)

I can't watching it while I'm doing another activity.

I need to put my entire attention on it to understand the wholall of the gossip, hahahha.