As tarawih needs to be prayed after the Esha prayer, it is compulsory to pray Esha before one starts performing tawarih. One can pray Esha by themselves first before joining in with the tarawih. However, as with all other prayers, this should not be rushed and each word pronounced distinctly and each action given its due.
According to some views (not the Hanafi view), it is possible to join the tawarih prayer with the intention of Esha, and complete a further two units when the imam makes salaam, and join in with the next set of tawarih.