Family visit rejected!

If, as you say, your entire family lives in Germany, then it does not take any great leap of logic for a consular officer to assume that you would prefer to stay with them rather than return to Algeria. As an applicant for a stort-stay visa, it is your task to provide evidence that refutes that assumption.

It doesn't sound like it will be easily possible for a student to refute that assumption. Having a significantly well-paid job in Algeria would probably suffice; having a family there who depend on you and a stable job that allows you to provide for them without going abroad probably would too. As a student, though, you're probably out of luck.

But your description sounds strange. If your father is a German citizen and you're not, it must either be because you have lost German citizenship acquired at birth, or because your father achieved German citizenship by naturalization after you were born -- but in that case it is strange that you and your mother were not included in the naturalization (at least according to Wikipedia's description, spouses and minor children will usually be naturalized at the same time).

So there seems to be something unusual going on here, and you (or your family) should probably consult a German lawyer specializing in nationality/immigration issues to find out if there's something that needs fixing there. In any case, it is probably not something random people on the Internet will be able to help you with.

Like Henning, I think you and your father should look into the citizenship question, but that requires a specialized lawyer.

In the meantime, perhaps your father qualifies for signing a Verpflichtungserklärung. It is a promise to reimburse the German state for any costs if you overstay, intentionally or unintentionally. This requires a sufficient income to pay for you and for any other dependents he may have.