Jennings hit the winner against Nottingham Forest on Saturday.
He said: "I learnt a lot. The German style of football is a lot different and it's good to add different parts to your game.
"I was injured for nine months in my first year and I just knew it wasn't meant to be.
"I had a year left on my contract and I wasn't really getting in and around the first team as much as I'd have liked.
"For my career, I thought it was best to come back home instead of wasting another year.
"The experience will stay with me forever. A lot of people ask if I regret it but, even though it didn't go as planned, I'll never regret a second of it. I'd have regretted it more if I didn't go.
"I'm happy I went. I gave it everything I could. It's just the injuries. I had a bit of bad luck. Hopefully I can do well over here and I can push on."
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