Questener: my friend says that it's also correct to say "I'm going to a cinema", then what's the difference with "I'm going to the cinema"?
Answer: it really depends on what the speaker means. If you're speaking of a cinema that's already been mentioned or is clear from the context in some way, or if there is only one cinema in town, then "the" WOULD be the correct form.
Here why is the clause "if there is only one cinema in town" in the present tense if this sentence is conditional type 2? Why not "if there were only one cinema in town"? I also wonder what the function of "would" is here? The speaker mixs tense, therefore I'm a bit confused by the use of "would" also here.