Which one did you use when sliding the fees to the cheaper static, ETA or Mempool?
If any of these, even after sliding it to the cheapest, still results in a high transaction fee, the above post may be correct, you have a large number of uTXO, which increases transaction size and leads to an expensive miners fee.
If you sent $300 in BTC from Exchange to this wallet and you just want to spend less than that, I think to lower the transaction fees you need to enable the coin control
- View> coins and then go to coins tab,
- then right-click any coins under that tab (below the amount you want to send),
- then choose coin control.
You can now create a transaction under the send tab, and other uTXOs and small uTXOs will be ignored. You should notice that the transaction size is much smaller and the transaction fee is much lower than before.
Edit: oppssss... Charles provided the same answer, but I added the ways to enable coin control.
Reference guide:
Source: screenshot by me and wallet, not mine.