Do they mean the same thing? And which one of them sounds more natural?

1) I learned through hardships under my belt in my youth that having money can greatly alleviate many challenges.

2) I learned through difficult experiences firsthand in my youth that having money can greatly alleviate many challenges.

Question

Do they mean the same thing? And which one of them sounds more natural?

1) I learned through hardships under my belt in my youth that having money can greatly alleviate many challenges.

2) I learned through difficult experiences firsthand in my youth that having money can greatly alleviate many challenges.

Answer

They both have issues, but the second one is clearly the better of the two.

In the first, "hardships under my belt" is a mixed metaphor that sounds like that's where the hardships were physically located. Also, "under my belt" is much more informal in tone than the rest of the sentence.

In the second, "firsthand" is redundant after "through difficult experiences."

"Hardships" and "difficult experiences" are roughly equivalent, but I think "difficult experiences" fits the tone better and is more descriptive. I would recommend that you use the second one but eliminate "firsthand." Alternatively, you could keep "firsthand" and eliminate "through difficult experiences."

Answer

Both sentences are grammatically correct and convey the intended message. However, for a more natural-sounding sentence, the second option with "firsthand" is slightly preferable.