Tendering your shares means you agree to the price of $6.44 + CVR payments. If they get 51% of shares to tender, then it doesn't matter if you personally like it or not because the majority rules (more or less, but you do have legal options if you really wanna try to fight it...good luck). If the majority of shareholders agree to the deal, then the deal happens regardless of what the minority want.
If you're not happy with the price, don't accept the tender offer. If 51% vote against the offer, it's possible they get another higher offer from Lundbeck or maybe someone else....or a lower offer....or maybe no other offer at all. Risk is the name of the game.
Just know if the tender offer is accepted by 51% of shareholders - you're pretty much locked into that same deal. Your shares disappear and you get $6.44/each with the potential for $1.50 in CVR payments. Doesn't matter what your vote was. You don't get special treatment based on your own vote - the majority's opinion is the only thing that matters.
Best of luck