"Do you have a pen?"
Translation:Ти маєш ручку?
No. It should be «ви маєте».
«Має» is the 3rd person singular form, «маєте» is the 2nd person plural form.
Different person have different ways to speak politely. In Ukrainian (and Russian; and, as far I know, in French), you show politeness by using a plural forms. I.e. you're talking to one person as if it were several person. Probably to show that you value their opinion more than just one person's opinion. So, «ви» is 2nd person plural pronoun, and it should be used with 2nd person plural verb forms.
You might be accustomed to some languages where you use some polite noun and a 3rd person verb form (like Portuguese você coming from vossa mercê 'your grace', or Polish using pan/pani, originally 'a member of nobility'). So, in these languages you say 'Does the member of nobility have a pen?', and don't address people directly. This is different from Ukrainian.
(In fact, Ukrainians can sometimes use the Polish word пан this way. Especially in an expression «про́шу па́на» (masc.)/«про́шу па́ні» (fem.) 'Please' (literally '[I] ask the member of nobility...'). However, this expression is mostly confined to the Western Ukraine, while «будь ла́ска» (literally 'be kind') is an universal way of saying 'please'.)