I bought on https://coingate.com/ , i pay 11 500€ of bitcoin, i never have problem until now.
They said :
" Bitcoin users across the network may notice their transactions sit as unconfirmed or pending for a longer period of time

Let me explain that every bitcoin transaction that's sent flows into what's called the mempool (short for memory pool) before it can be confirmed by miners. When there's a dramatic spike in transaction activity, the mempool can become congested because so many transactions are waiting to be included in the next block. "