check tenses please

I am writing this to you to thank you for being my best friend.
 
I met (have met?? why?? because you are talking about past) you approximately five years in the  *** University's bookstore and since then, you have been standing (have been is also possible) by my side talking to me whenever I need a friend and giving advice when I need someone to tell me what might be the best way to approach something -- thank you. I have noticed that your look (what doest it mean?) has changed (changes possible too) too, which I have noticed at our last gathering (it would be good to change sentence a little bit, it sounds  ). We aren't able to do anything about the passing of time, are we? Ha. ha. Come to think of it, if we hadn't met five years ago, I might have been doing something different that I am doing now .which, if I care to fathom, might not be so desirable in terms of the amount of money I can make I think the type of friends a person has can make  a big difference in that person's life; it might not be just the passing words, "Friends make a man." I just made those words up.  (It's impossible to understand that at all. I would advise you to write in more simple way until you get enough knowledges to use more complicated construction.)
Anyway, holidays  are coming up and there will be my birthday. Just it happens, my birthday is on one day of the holidays, on ***, *** (it sounds odd too). Would you like to come? If you decide to come, I will be able to meet and give you the key chain you left behind at the gathering and we can celebrate my birthday.

Haven't you had a car still? If you don't, let me know, and I will be able to go to your place and pick you up.

I hope to see you at the party.

Best wiishes,

It would be more useful if you rewrite it at all in a new way in grammar and narrative construction.