are the sentences correct?

[KLPNO]

Hello everyone
I'd like to ask if the following sentences are grammatically correct.

Not all employees of the Section dealt with international standards at their
previous work knowing only the requirements of the normative documents of XXX. So they have to learn to work based on the international standards.

 

[Tdol]

I'd put a comma before 'knowing' and change the second to this: So they have to learn to work to international standards.

 

[KLPNO]

I'd put a comma before 'knowing' and change the second to this: So they have to learn to work to international standards.

Thank you very much, Tdol.