Learn Spanish (Spain): ¿Tenéis alguna duda?

The word alguna must match the gender and number of the noun it describes, which in this case is the feminine singular noun duda. The shortened form algún is only ever used before masculine singular nouns (like algún problema).

The English translation says "any doubts" (plural), but alguna duda is singular. Why?

When asking a general "Do you have any...?" question, Spanish strongly prefers the singular form. You will hear ¿Tenéis alguna duda? (literally: "Do you have any doubt?") much more often than the plural ¿Tenéis algunas dudas?.

In English we usually ask "Do you have any questions?". Can I use pregunta instead of duda?

Yes, you can absolutely say ¿Tenéis alguna pregunta?. However, in Spain, it is very common for teachers, presenters, or guides to ask if you have alguna duda (literally "any doubt") to check if you are confused or need anything clarified.

Who is being addressed with the verb Tenéis?

Tenéis is the vosotros form of tener (to have). In Spain, this is the standard way to address a group of people informally, like saying "you all" or "you guys". If you were asking just one person, you would say ¿Tienes alguna duda?.