Pasting data from Excel table takes very long
You don't need to write code. Just use the Data Import/Export Wizard.

Right-click on the database in SSMS, go to Tasks and Import Data. Select Flat File Source as your data source (because you're using CSV), and then browse for the file. Click next, select the database and the target table. You'll need to check the mappings for the CSV columns to the table columns (making sure the CSV column headings are the same as the table columns helps with this), and you can preview the data to make sure.

If everything is correct, click Next, Next and Finish to import the data. If there's an error, it'll tell you what it is (sometimes slightly cryptic though).

As a note though: I'd advise against trying to copy/paste/edit data in the Table Edit window. Writing SQL statements is a much more effective and time efficient way of doing it (or using the Data Import/Export Wizards).