I´m back!!

After good [you could also use 'enjoyable] holidays I returned to real life. [you could use a more active phrase like 'I returned to real life after taking a good holiday/some good holidays']. 
Today it is my first day at work and I have so much many things to do :( but this is for a good reason, as I was in on holidays.
I was at the beach with my family,. I've had 4 years without being able to go with my family on vacation and definitely, this year I have been was able to go with them. [you could also write 'Until this year, it had been four years since I last went on vacation with my family'].  
One part of this my family are in from Seville [or ' Part of my family lives in Seville'] so it´s too dificult to see us eachother because we have lot of work and differents obligations and schedules, but only once in a year, we got get together to go to the beach ever.
I have been going to Benalmadena since I was a baby and it´s nice to come back there for a week.
I've played, I've eaten, I have and bathed much  and I have spent lot of time with them/my family. also I also celebrated my birthday there so they have been a wonderful holidays.

Now I have to work and continues with my bad English.

Rocio, your English is excellent. I just made a few little suggestions for improving the structure. I wish you all the best with your English. I'm sure you'll reach a really high level. Best of luck!