309 sat/byte is not a low fee, it's actually pretty high at the current moment.
To check the current fee prices, go to
https://jochen-hoenicke.de/queue/#24h and look at the pending tx fee and mempool size, check higher brackets to know what fees are getting accepted within next blocks. In Tools->Preferences you can enable manual fees, which can be recommended for more experienced users to avoid overpaying on fees. In worst case scenario, if your fee is way too low, it will get stuck for a few weeks as unconfirmed, and will either get confirmed if the mempool will be clearing, or will get evicted from mempool and return to your balance.
