I am working with a web application, there is a case to use 4 different buttons in one place with different functionalities. I think adding all the buttons in one place leads users see awkward and may cause user experience. What would be a better solution for this from UX and UI perspective?
One thing you can do is redesign the buttons so that they dont look similar. In your image, the filter and edit are almost identical in design. If you redesign them so that they are primary, secondary, and tertiary designs, the user may be less confused on what button does what.
As a side note, I recommend removing the term "flight" from your buttons as they seem redundant. The buttons could read "Filter", "Add New", "Edit", and "Delete" in order to get rid of some text. If the user knows they are looking at flights initially, they don't need to be reminded when reading each button.
This situation is the same as in actions within a table and in each row, the way to differentiate both actions is by using buttons in the general case and icons in the individual case:
It would be interesting to see what you have on the left. I see part of a search box, which makes me think there are other controls there. And an important point is that most flight search sites have all the controls in the left column. There are some that arrange the controls at the top (Google Flights, for example); but no matter where the controls are arranged, they are always together.
Either way, even without seeing the left panel, I am pretty sure that's where the problem is. I mean: If you can search, you want to filter the results and use the facet search, right? Then why would the filter button be on the opposite side of the screen?
The same is true for "Add New Flight." The list is the result of a search, so you are probably going to add NOT a new flight, but a new destination. And if that's the case, it needs to be done with the rest of the information.
Again, I can only guess since you have truncated the information, but that's more or less how most airlines work.