Need help with understanding spot trading.

Hi guys! I’m struggling understanding something. Let’s say I have 30k$ and all I want to do is buying BTC at the price of 110k$ (CAD) and sell it at 115K$ (CAD). What exchange or app let me to this without making my profit zero… Kraken to buy 30k$ worth of btc with a custom order it’s almost 1600$ fee. Please need help me understand how it works! All I want to do is to put let’s say 30k$ and buy low and sell high, reinvest the profit. I don’t if I’m clear or not, sorry for the fault, English is not my first language.

Thanks to all answers in advance, I really appreciate!!