poslovati

1. (of a company, bank) to operate; to do business
   Firma već tri godine posluje s gubitkom. — The company has been operating at a loss for three years.
   Banka posluje od osam do šesnaest časova. — The bank is open from eight to four.
2. (with someone) to do business; to deal
   Godinama poslujemo sa partnerima iz Nemačke. — We have been doing business with partners from Germany for years.

The partner is expressed with s + instrumental: poslovati s firmom.