Mulatu Fekadu Zerihun - There should not be any confusion between research gap and problem statement in academic studies as the two terms are different in meaning and context. Research gap refers to the gap in the existing theory and practice. Gap could be seen after extensive literature review and if there is no gap your research questions had already been explained by others and by continuing there will be only duplication of work.
Problem statement: Once a researcher finds a research gap, the next step is the formation of problem statement. A problem statement is a description of research gap and can be constructed based on research gap which researcher aims to answer and it clearly communicates objectives of research. It is a definite or clear expression [statement] about an area of concern, a condition to be improved upon, a difficulty to be eliminated, or a troubling question that exists in scholarly literature, in theory, or within existing practice that points to a need for meaningful understanding and deliberate.
A gap talks to the need for the research. Having reviewed studies and examined theories, one identifies a gap-- that is, the need for research. And the existence of the gap means that there is a problem that needs to be solved.
Identifying a problem is not sufficient to conduct research-- there must be a gap as well. A good research problem must fill the void/or gap.