Learn Hardcore German: Kannst du mir den Beleg senden?

In German yes/no questions the finite verb moves to the first position. So you invert Du kannst (you can) to Kannst du (can you) to form a question.

Why is it mir and not mich?

mir is the dative form of ich (I), used for the indirect object (to whom something is sent). mich would be accusative, but here you’re not the direct object; you’re the recipient.

Why is den Beleg used instead of der Beleg?

Beleg is masculine (der Beleg). As the direct object you need the accusative case, so der changes to den.

In what order do mir and den Beleg appear, and why?

Personal pronouns in the dative case generally come before full noun phrases in the accusative. So mir (dative pronoun) comes before den Beleg (accusative noun).

Why is the infinitive senden at the end of the sentence?

In German, finite modal verbs (kannst) occupy the second position and push the main verb in infinitive form to the end of the clause.