Im always wondering how things will continue when all of them are mined
Look at testnet3. There are still some new coins produced, but fees can sometimes be higher in sat/vB, than on mainnet. I guess if worthless coins encouraged users to pay so high fees, then worthy ones will do so as well.
but how is the bitcoin network gonna confirm transactions when there is no mining to be done?
There are some reasons to mine new blocks, even if the coinbase amount is equal to zero. For example: to unlock previously timelocked coins (because of coinbase maturity, other regular transactions with locktime, and so on). Also: if nothing else, then notarization and timestamping of things is one of those use cases, which can work without any coins.
Is it a matter of everyone just running a node instead ?
If some miners will leave, then other miners will take their place. The minimal difficulty is CPU-mineable. And even on test networks, where coins are worthless, there are ASICs. Many people will just keep mining anyway, no matter what, for example because they have a choice: waste some energy, or use it for mining (so they keep mining to avoid that waste, and do something with that overproduction).
or is it like that miners will get the transaction fee instead?
Fees will be higher in the future. Also because if there are many fees, then you can pay someone in your coinbase transaction, and if you align all amounts properly, then nobody can find out, which fees were used for payment, and which were just claimed by the miner.
For example: if you have testnet4, and you want to send someone 50 tBTC, then you can of course make a regular transaction. But: if you instead mine a coinbase transaction, and put the recipient's output there, then nobody will figure it out, what was the previous address, and who exactly did it.
how honest will it be as in will the fees be super high will it be self regulated?
Those, who will stay on-chain, will use direct payments, and will pay high fees, because of limited space. Those, who will use second layers, will batch their payments with a lot of other people, so a fee per user will be lower. For example: if you have Alice->Bob unconfirmed transaction, and it pays 1000 satoshis, and then you have Bob->Charlie transaction, also paying 1000 satoshis, then you can just create Alice->Charlie transaction, paying 2000 satoshis, and taking less space (so also having higher sat/vB rate).
the more transactions there are the higher the fee will be?
If you have a minimal transaction fee of 1 sat/vB, then yes, more transactions simply means higher fee. And to fit all of that into blocks, and confirm in 10 minutes, it will have to be batched. And the obvious consequence of batching, is seeing a single transaction, paying more fees, and serving more than a single user. So, from the perspective of the current software, fees will be higher. But: the fee per user can be the same or lower, if transaction joining will work properly.
