The first sentence is almost correct (but you still need a capital I and a period at the end). "Because is the subordinating conjunction used to connect two clauses. (= your sentence number 1). You can also use "because of" to connect a noun phrase to a sentence. "Cause" is either a verb "to cause" or a noun "the cause of the accident". It cannot be used as a subordinating conjunction. A lot of people get this confused because of the internet/chat writing. The spellings "coz" "cuz" , etc. are not correct. I think they get the sound "cause" in their ears and that makes it come out in writing incorrectly.

The first one is almost correct, in that you have missed the capital letter for "I" and the fullstop (two things which the Chinese seem to be exceptional at). The second sentence is 100% WRONG! This is because the word "cause" can be a verb or a noun only.

first sentence is right!

*as I watch quite a lot..

Second is correct in everyday speech, first is correct in any case. Actually native speakers answered second was incorrect, but a lot of people who speak English(well, at least in America, as I quite a lot American videos) will use cause in this case.