Foreign workers [occupy a large portion in] the company.
Mexicans [occupy a big portion of] the USA population.

Do these sound natural?

Thanks in advance!!!!

Question

Foreign workers [occupy a large portion in] the company.
Mexicans [occupy a big portion of] the USA population.

Do these sound natural?

Thanks in advance!!!!

Answer

Not really. 
Foreign workers make up/represent a large proportion of the company's workforce.
Mexicans make up/represent a large proportion of the USA population.

Answer

Editor Anna gave a good answer.

Answer

both sound natural.