What part of speech is behind the accusative in English? What part of speech is behind gerund?

Verb+accusative

Preposition+accusative

Be+doing (continuous)

Verb as the subject, starting from doing.

Preposition+do

Be doing sth.

Have ...+do

Sensory verb+do

Practice doing, finish doing, like doing, mind spending ... stop doing (forget to do something) remember to do (remember to do something)