My holiday.

During In the month of September I my was at holidey (holiday). I flew by plane in Spain (I flew to Spain by airplane). I wery very glad (happy/excited) about my trip. I lived in a small taun Santa Susanna on coast of Santa Brava. I visited the museum of Salvadora Dali, and the architect park architektor of Antonio Gaudi, mountain Monserrat Mountian, and watched a flamenco show. <flamenko>.

When writing don't forget to keep your tenses the same, if you start in past tense keep it that way, and articles are also important don't forget those as well :-) 

My holidays. 

I traveled in September. I flew on an airplane to Spain. I was very glad to make a trip. I lived in Santa Susanna. It is a small town located on the Santa Brava coast. I visited the Salvador Dali Museum, a park made by architect Antonio Gaudi, mountain Montserrat. I also visited Flamenco show. 

Возможно, тут тоже море ошибок :) 

Corrections in red.  Stylistics in blue.

My Holiday.

In September, I was on holiday. I flew by plane to Spain. I enjoyed my trip very much.  I stayed [1] in the [2] small town of Santa Susanna on the Costa Brava. [3]  I visited the Salvador Dali museum, a park designed by the architect Antonio Gaudi, visited Mount Monserrat, and also attended a performance of flamenco music.

[1]  When you visit a place for a relatively short time, you "stay" there; you do not "live" there."  

[2]  Santa Susanna is a specific town; therefore, use the definite article "the".

[3]  Even in English, we call the coast by its name in Spanish.