How to describe correctly?

"I was also handling a role of main logistic specialist in the biggest polish company in welding branch. It was a role where I have learned how the supply chain works on a worldwide scale"

I would suggest the following amendment:

"I also worked as the main logistics specialist for the largest Polish welding company. It was a role which taught me how the supply chain works on a worldwide scale."

How to describe this correctly?

Hi,
I'm trying to write my cover letter and I have problems on how to describe my previous role. I'll paste it here and what I have already wrote. But only to describe what I want to say (because I know it's incorrect):

"I was also handling a role of main logistic specialist in the biggest polish company in the welding branch. It was a role where I have learned how the supply chain works on a worldwide scale"

Heres some background for you. I want to apply for a Purchasing Assistant job in a trading company. Especially since I'm wondering about the first sentence. Despite that I basically know a little English . I would not like to make any stupid mistakes especially in the cover letter :)

Thank you in advance for you help :)