- How do I make myself untraceable in the network? That is, how do I get my BTCs to a new address, that is not linked to my ID via the KYC exchange?
You can't make yourself untraceable. You can send them through CoinJoin or mixers which can break the link. You must ensure that you do not mix your addresses and thereby forming a link.
Centralized KYC exchanges are known to block and ban accounts which deposits money from a mixer. You should take this into consideration as well and avoid spending funds linked with mixers to your exchange addresses.
- How do I keep the costs as low as possible?
Consolidating your inputs could help:
https://bitcointalk.org/index.php?topic=2848987.0- What would be the best storing solution for long term BTC storing? I guess some kind of an multi-sig solution would be the best?
Multisig isn't more secure than cold storage. You should ideally invest in a hardware wallet or setup a cold storage. If you're inexperienced in this domain, I recommend using a hardware wallet for a foolproof method of storage.