So I bought for 400eur worth of bitcoins BCH (bitcoin cash) and I was supposed to send my seller 160eur in total. We agreed on half before delivery of physical goods and half on delivery.
You have BCH. You are sending 80eur (half of 160eur) in BCH to your seller.
the question: were you seller asking for BCH payment or BTC payment?
The first time I sent I messed up with the BCH conversion so I ended up sending him only 0.00873BCH = 11.44EUR. So I sent a second time this time 0.060057BCH = 78.68EUR. I got 62 Blockchain confirmations for both transactions.
if he's asking for BTC, 0.00873 seems right amount for 60eur in BTC but you sent him BCH
I think it's not seller fault here, you might be wrong on the BTC or BCH payment requested by the seller
can you give us more information about the transaction you were conducting?
an invoice or email or any writing of him (seller) requesting the
payment method and amount