Incorrect statement about $Ge$ is:
A. $Ge{{O}_{2}}$ is weakly acidic
B. $Ge{{\left( OH \right)}_{2}}$ is amphoteric
C. $GeC{{l}_{2}}$ is more stable than $GeC{{l}_{4}}$
D. $Ge-Ge$ bond energy is lesser than that of $Si-Si$

Hint: Germanium belongs to the 14th group of the periodic table which belongs to the Carbon family. Its atomic number is 32 and belongs to the 4th period of the table. The major property of this group is catenation which means they operate in the +4 oxidation states. Germanium and Silicon are both semi-conductors in this group.

Complete step by step answer:
When we analyse the statements one after the another then we will be able to attempt this question, in the A. part it has said that $Ge{{O}_{2}}$ is weakly acidic. Let us check the statement by reacting it with the water to see the product it yields.
$Ge{{O}_{2}}+2{{H}_{2}}O\Rightarrow {{H}_{4}}Ge{{O}_{4}}$, this product is weakly acidic therefore, the first statement is the correct one. The next statement says that $Ge{{\left( OH \right)}_{2}}$is amphoteric which is true statement again as the hydroxides of Germanium are all amphoteric and that too because it is a metalloid also. The next option C talks about being $GeC{{l}_{2}}$ more stable than $GeC{{l}_{4}}$, this statement is incorrect as we told above that Ge belongs to the carbon family where the tendency of elements being in +4 oxidation state is more as compared to the +2 state in $GeC{{l}_{2}}$, therefore $GeC{{l}_{4}}$ is more stable.
In the option D, it says that Ge-Ge bond energy is lesser than that of Si-Si which is correct as we move down the group from the top the bond energy decreases and Silicon comes before the Germanium, therefore, the bond energy of Ge-Ge bond will be lesser than that of Si-Si.

Hence, the incorrect statement about Germanium is C.

Note: The Bond energy decreases when you move down the group because the size of the atom increases and there is less attraction from the nucleus, therefore, the bond can be broken easily with less amount of energy.