Doubt on BigQuery [Poor GUI interface]

[Kudos]

Please address the following issues:

1. How we can upload multiple files (CSV) from our PC to the dataset in one attempt, I saw there is no way to do it from GUI we can do one at a time.

2. Why we can't export a dataset from bigquery to Google cloud bucket storage directly or locally on our PC, why there is no such feature, I saw we can only do a table one by one like a stupid.

3. What is the extension of the dataset that google cloud storage uses, and can we convert group of .csv files into a dataset and directly upload it as a dataset for making queries in bigquey.

4. Can we export a dataset to local PC and then reupload it under a same project by renaming it?

Please suggest a method if it can be done anyhow by GUI or code or GC terminal or anyhow, I really tried doing it but failing it's very important, I will be thankful for suggestions for my whole life.