Here's a correction of your text, JuanJo.
I usually go to the beach. I go to the Mediterranean sea, because I have an apartment near the coast.
I
travel abroad once a year. I travel to different countries because I
want to get to know different cities and cultures around the world. I prefer
to travel in Europe, because it's near to Spain and it's cheaper than travelling outside Europe. When I travel abroad, I usually stay approximately five
to seven days. When I go to the beach, I stay two or three days in
spring, several weekends, and from ten to fifteen days in the summer
holidays.
When I travel abroad, I usually book my travel online because it's cheaper, faster and you can find a lot of offers on the web.
Please ask if you would like me to explain any of the corrections.