Self tax filing

Hello,
I am a tax resident here, currently working as a company employee on an Engineer visa. Until now, I have not filed an income tax return myself because my employer deducted income tax and paid social insurance on my behalf. However, I now have additional sources of income, so I would like to file my income tax return myself and, if possible, ask my employer not to deduct income tax and resident tax from my salary (and, if possible, social insurance premiums as well).

Is this possible, at least for income tax and resident tax?

If this is not possible, will my employer deduct income tax and resident tax from my salary based on my combined income, or only based on my salary income?

If anyone has experience with this, I would appreciate your guidance.

Thank you.

by Ok_Iron4357