English questions, please help?

I've known him for 10 years.
(is this sentence correct, how would you normally say the same thing?)

I heard hes coming to the party tonight.
(should this be "I heard he was" or "I heard he is", and please explain why)

i have no credit in my phone. /i have no credits in my phone.
(credit or credits?)

His writing skills is not good/ His wiritng skill is not good.
(skill or skills here?)

I write a diary every day,
I write diary every day.
(how do you normally say this? )

Thank you very much. I deeply appreciate for your generous help!