How can i access tons that are in my jetton contract type wallet (smart contract address), is that even possible? Or how can i transfer these tons in smart contract after SM receive it

If you are using Jetton Transfer, you can specify an address in the response_destination (the address where to send a response with confirmation of a successful transfer and the rest of the incoming Toncoins). This way, the remaining funds can be transferred to the address you designated. For more information, you can refer to the following link:
https://github.com/ton-blockchain/TEPs/blob/master/text/0074-jettons-standard.md

well im still having some problem understanding the concept, like i want to just create pre-sale functionality so user can send TONs and get my jettons basing on fixed rate with max pre-sale supply being 15%, i tried making that in minter, but minting tokens for user and burning the rest to stay at the same supply level don't seem reasonable

I wrote something like this in wallet.fc but im not sure if it's correct https://mystb.in/PowersellerSupervisorsPichunter