I think his Japanese has improved quite a bit, hasn't it?

I am busy with work during the daytime.

Software engineering is a field of study related to the design and development of computer programs.

I am learning how to use the present participle in English.

The present tense is used to express things that are happening now or general facts.

This system needs reconfiguration.

He reconstructed the broken house.

All members of our team are experts.

Constructivism is an educational theory that knowledge is actively constructed by each learner.

He has already finished writing the report, so we use the present perfect form.