I guess because my bitcoin in spot value in dollar will increase if the market is going higher but I am losing the value in future trading because I go short, the value in dollar will remain the same?
If I understood you correctly, you are SHORTING BTC/USDT pair on the Futures Market, am I correct? If yes, then you are losing money on the market rather than winning it. Choosing between LONG and SHORT, will serve as your identifier for making a directional bias.
LONG means that your directional bias is for the assets' price to go up while
SHORT is the exactly the opposite.
Also if the market price of bitcoin decrease, I will be losing value in dollar in spot but the future favours me. This also means the value will be the same?
Exactly. However, I can't understand what you mean by the "value being the same".
In FUTURES, as far as I know, there are two types of futures contract;
COIN-M and USDT-M Futures contract. COIN-M basically means that you are using the crypto itself as your collateral, and that if you are shorting BTCUSDT pair, you are increasing the quantity of your BTC when price goes down.
On the other hand, USDT-M uses USDT as your collateral againts BTC, so if your shorting the market, you are increasing the quantity of your USDT instead of BTC if the market structure is in downtrend.
Hope it answers your question.