I work for a big group of companies and handle the purchases for it.
1) A lot of times suppliers offer gifts as cash in return of favour for hiring them as suppliers, is this cash halal?
2) Extension to this question is if I can open an external company and consider it as supplier company and then supply goods to my own company where I work and take salary from and earn the extra money by taking lower rates from suppliers and offering on slightly higher rates to my company.

1) If one doesn't ask and he receives such gifts it is allowed.
2) If this is allowed in company laws or the law is silent then it can be done otherwise one can ask someone else to do so not himself.