Learn Swedish: Några av dem måste tacka nej till inbjudan om de inte heller hinner. - Some of them must turn down the invitation if they do not have time either.

This part of the sentence starts with om (if), making it a subordinate clause. In Swedish subordinate clauses, sentence adverbs like inte and heller must be placed before the finite verb (hinner). If this were a main clause, the order would instead be de hinner inte heller.

Why is the order inte heller and not heller inte?

When these two adverbs appear together to mean "not either", the standard order is strictly inte heller. In subordinate clauses like this one, they act as a unit and move together as a single block before the verb.

How does the expression tacka nej till work?

It literally translates to "thank no to", but it is the standard Swedish phrase for "decline" or "turn down". You must use the preposition till to connect it to the noun being declined, which in this case is inbjudan (the invitation).

The English translation says "do not have time", but Swedish only uses the verb hinner. Is a word for "time" missing?

No, Swedish has a specific verb, hinna, which inherently means "to have enough time" to do something. It does not need the noun tid (time) and can stand completely on its own.