500 and 504 error messages

When i go to my website it returns a 504 error message , a couple days ago it pop up a 500 error message and now i can not even login to the dashboard . i just finished uninstalling and reinstalling wordpress for the second time and i had barely even begun building the website .

what is going on? . does this type of thing happen all the time with wordpress ?
this is for a client and is the third time i have built this website !
I am so stuck i don't know what to do and i have got to have this done by tonight .

Can you help me?
greenpagesbc.com