Chinese is very interesting!... Just "I miss you" this sentence, you can say it in some ways.
For example:
"我wo想xiang你ni(們men)"
"好hao想xiang你ni(們men)喔oh!"
"想xiang念nian你ni(們men)!".
And there are also a lot of ways to say "my friend" in Chinese:
我wo朋peng友you,
親qin愛ai的de(my dear - my darling)
so you can say: "我的朋友, 好想念你喔!" or "我想你, 我朋友!"
or "親愛的, 好想你喔!"