When is a will valid?
The author of the will must be able to testify, § 2229 BGB. To do so, the author must be at least 16 years old and capable of doing business. In that case, he can write a will together with a notary. If he is 18 years old, he can make a will completely on his own. A personal will (§ 2247 BGB) must be entirely handwritten and signed. It should also be dated and the place of erection indicated. However, missing information does not necessarily lead to nullity if the place and date of the establishment can be determined otherwise, § 2247 V BGB.
A notarial will is made by the deceased declaring his last will to the notary or by giving him a will. The deceased may hand over the will open or closed; it does not need to bewritten by him personally, § 2232 BGB.