Learn Russian: Давай работать вместе.

Давай is used when you are speaking to one person whom you address informally (using ты). If you were suggesting this to multiple people, or to someone you address formally (using вы), you would say давайте работать вместе.

Why is the infinitive работать used here, rather than a future tense verb?

When you use давай with an imperfective verb (like работать), you must use the infinitive. This structure is used to suggest starting an ongoing, continuous, or habitual action.

How would the sentence change if we used a perfective verb to mean 'Let's work for a bit'?

With perfective verbs, you cannot use the infinitive after давай. Instead, you use the 'we' form of the future tense. So, if you used the perfective verb поработать, the sentence would become Давай поработаем вместе.

Does давай mean 'give' here?

Literally, yes, it is the imperative form of the verb давать (to give). However, in this grammatical structure, it acts entirely as a fixed particle meaning 'let's' to suggest a joint action.