I’m also a new seller (though I’ve sold on Amazon for an employer for 10 years I worked for previously. I now work for someone else who hired me specifically for my Amazon knowledge!)
The reserve will eventually dwindle to nothing. It will increase slightly as your sales increase, but will eventually dwindle to either a very small amount. My reserve the first payment period was over $400 and was basically all my sales. This payment period, I still have a reserve of about $105.
Basically, your first payment period, I’d expect to get nothing. They’re going to hold it in reserve. Then, slowly over the next pay period, it will mostly become available. You just got to prove you’re not a fly by night operation.