However, I'd like to know if there will be BTC miners once the supply is fully mined, and will the fees for sending from wallets to exchanges be high? I also wonder if the price fluctuations will be similar to the current bearish and bullish market. Currently, BTC is widely traded, buying at a low price and selling at a high price. But will BTC trading be possible in the future, similar to daily trading? I think this is worth discussing...

Day trading will always exist in the Bitcoin market as long as there are sellers and buyers through any exchange. The only difference will be the price and daily trading volume of Bitcoin itself. Because when all Bitcoin is mined, most people will be very aware that the price will be much higher and will not recklessly sell in large quantities, although trading will continue in the market due to the constant supply and demand for Bitcoin. As for the shipping costs themselves, I think they will continue to vary because they are also influenced by the number of transactions occurring simultaneously.
There is, as long as the transaction keeps going.
The cost depends on how congested the network is.
It depends on the law of supply and demand regarding price fluctuations.
The scarcity of Bitcoin once the total supply is reached will have a positive impact on the price, which is expected to get more expensive and of course all things that will happen to Bitcoin in the future I say based on speculation, not certainty.
Do more research before jumping to conclusions.
I also agree with your comment because every time a transaction is executed and successful each day, there will still be a transfer fee. Meanwhile, Bitcoin's price fluctuations will continue, as we have seen before, so Bitcoin's price fluctuations will continue to be visible even after Bitcoin has been mined. The influence of supply and demand on Bitcoin will always trigger changes in price and daily trading volume, as Bitcoin is now being sought after and eyed by large companies and certain countries to buy and hold as a valuable asset.