You do NOT put yourself on payroll.

You need to go to a tax professional to fix your errors.  If you made a significant mistake that like, you likely have other issues that a tax professional can help you with.

You cannot pay yourself a salary as a Single Member LLC, unless you made the S Corp election.   You cannot deduct any payroll expenses on a schedule C.    I would suggest you consider making a late S Corp election and back date it to when you started payroll in 2020.   Hopefully the IRS accepts it.  Otherwise all of your payroll would be treated as income, except the taxes  you paid.   Contact your payroll provider to see if they can assist you on the payroll issue, before you file your tax returns.   You may need to file an extension on your taxes till the issue is resolved.

Do NOT make an election to be taxed as a S-corporation just because you made a mistake by putting yourself on payroll.  The decision to be taxed as a S-corporation is complicated and difficult, and you absolutely should NOT do that without the assistance of a tax professional.

"so the form 944 will work to deduct the expenses and salaries in schedule C?"

Everything about what you posted here is Wrong. Further, this is for using ProSeries software to prepare clients' tax returns.

You really need to find a CPA to help you fix whatever you did in 2020 for all that payroll, and whatever else you need to review with them.

Look at this similar topic:

https://proconnect.intuit.com/community/proconnect-tax-discussions/discussion/re-paying-taxes/01/138...