I love learning and reading about Islam, but I also know that we should acquire knowledge of Dunya, to be able to help ourselves, family and fellow muslims. But my problem is when I try to learn subjects of Dunya, I feel as if I'm cheating my Islamic learning time. What do you suggest I do?

Praise be to Allah, the Lord of the World; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

The Muslim is asked to spend his time in that which is useful for him and for his community. The Dunya (this worldly life) knowledge which is needed by Muslims is a communal obligation on the Muslim community in general. So, some Muslims should acquire that knowledge. If they do, the obligation is lifted from the other Muslims. If there are enough people learning those worldly subjects, the remaining people should occupy themselves in learning Sharia. Allah Says (interpretation of meaning): {… Say: "Are those who know equal to those who know not?" …} [39: 9]. Allah also Says (interpretation of meaning): {… rise up. Allâh will exalt in degree those of you who believe, and those who have been granted knowledge. …} [58: 11].
But if the knowledge the person wants to acquire is a means to assume his responsibilities towards others like spending on his children and wife and the like, he has to acquire that knowledge and make every effort to fulfill his duties. In this case acquiring worldly knowledge (Dunya) is given priority over gaining knowledge of Sharia that goes beyond the knowledge of obligations (religious duties).
It is a rule that when an obligation cannot be done unless something else occurs, that thing that is missing becomes an obligation as well. But if the person can gather worldly knowledge and knowledge of Sharia it will be better.
On the other hand, the Muslim should be moderate in everything and balanced. He should give everything the attention it deserves as far as possible.
Allah knows best.