но периодически приходилось посещат

но периодически приходилось посещать различные курсы, в основном, связанные с моделированием

Результаты (английский) 1:

but periodically had to attend various courses, mostly related to modelling

Результаты (английский) 2:

but occasionally I had to attend various courses, mainly related with modeling

Результаты (английский) 3:

But from time to time had to attend various training courses, in the main, related to modeling