What language are you speaking = ¿Que idioma habla Usted?
If you are speaking in (the language) Spanish it is Spanish. The national language spoken in Spain is Spanish.
Me gusta hablar su idioma
Yes, the main language in Mexico is Spanish.
When speaking of the entireity of the language, usually you would say "el idioma", or or less commonly "la lengua". When speaking of specific wording, as in "the specific language in this paragraph", use el lenguaje.
No, Portugal is not a Spanish-speaking country. The official language of Portugal is Portuguese.
Español
No, Venice is not a Spanish-speaking city. The primary language spoken in Venice is Italian.
Cuba is a Spanish speaking country because it was a Spanish colony.
There is no "Mexican Language." The official language of Mexico is Spanish. Therefore, speaking Mexican refers to speaking Spanish. However, there are also indigenous languages spoken in Mexico, such as Nahuatl and Mayan.
Yes, there are Spanish speaking countries in Europe. Spain is a Spanish speaking country. Also the language of Portugal is Portuguese which is very closely related to Spanish.
There are 21 countries with Spanish as an official language.
No, the Philippines has their own language called Filipino and the majority also speak English.