"This summer I would like to travel somewhere on holiday, but I can't decide where to go. Please advise me."
If you want to stay in Spain for your holiday, I would recommend San Sebastian in Northern Spain. The beach (La Concha) is lovely, as is the scenery around there.
In the Basque language, San Sebastian is called Donastia.
If you want to travel outside of Spain, then I recommend Ireland, especially the Northern part of the Island. The most Northerly part of Ireland is in Malin Head which is in the Republic. The Wild Atlantic Way takes in the entire West Coast from the South, in Kerry, all the way to the Inishowen peninsula, in Donegal.
The six North Eastern Counties of Ireland that make up Northern Ireland is also worth a visit. Currently, you can travel the entire Island of Ireland without noticing that you have crossed an International border. Brexit may change this. The Giants Causeway is in County Antrim, which is quite famous. Derry/Londonderry is a small city and has loads of history. The Biggest City is Belfast but is still quite small. The TV series "Game of Thrones" is made nearby and there are tours of some of the sites used in the series available from Belfast.
I hope you enjoy your holiday!