What are the implications for a person who committed Zina and his partner became pregnant and gave birth to a daughter, and he is now unable to do anything for them, knowing that he sends them a small amount of money from time to time? And is she (the daughter) his responsibility?

It is obligatory to repent to Allah Almighty for this grave sin. Whoever repents, Allah will accept his repentance. Sincere repentance fulfills three conditions: regret for the sin, determination not to return to it, and abandoning the sin. The girl who was born through adultery has no lineage to the father and is legitimately attributed to her mother. If you intend by the money you give them to seek the pleasure of Allah, you will be rewarded.