Based on the error message, you either didn't assemble the coinbase transaction properly or it is not the first transaction in the block which it must be. I'm not going to deconstruct your hex strings, nor do you provide the full block that you want to submit in Regtest.

Oh, and when you have an odd number of transactions in your block, you have to pay attention to properly assemble the Merkle tree, because one transaction has to be doubled for Merkle hash calculation.

Did you even try to read a bit in "Programming Bitcoin" as @j2002ba2 suggested. I highly recommend it to you, too!