Learn Turkish: Geçerli bir vize ile sınırı geçebilir miyim? - Can I cross the border with a valid visa?

Let's break it down! Start with the verb root geç- (to cross/pass). Add the ability suffix -ebil and the aorist tense suffix -ir to get geçebilir (can cross). To make it a question for "I", we use the separate question particle mi, add the buffer -y-, and attach the personal suffix -im. Together, that gives us geçebilir miyim? (Can I cross?).

Why is there an extra -ı at the end of sınırı?

That is the accusative case suffix. The base word is sınır (border). Because you are crossing a specific border, it is the direct object of the verb geçmek (to cross). Adding the -ı tells us it is "the border" being crossed.

Is the word geçerli (valid) related to the verb geçmek (to cross) at the end of the sentence?

Yes, it is! The verb geçmek means to pass or cross. With suffixes, it becomes geçerli, which literally implies something "has passability" or is accepted. In English, we just say "valid."

Could I combine vize and ile into one word here?