Whether the BTVG applies depends on the amount and timing of your payments and should be examined.
The Developer Contract Act protects buyers where more than EUR 150 per square metre of usable floor area is to be paid in advance before completion. If the advance payments remain below this or only fall due after completion, the protection of the BTVG may not apply. You then bear the risk alone under the general rules.
Have the contract and payment plan examined before you sign. This shows whether the BTVG applies and what security you are entitled to.