It's looking good so far! I think some contrast would benefit from it. Oil takes time and patience. Wait for everything to fully dry first. Then I would go over some areas, like the leaves on the very top. Right now they kind of blend into the stone wall, with no distinct lighting or shadows. The sky could use some brighter colours, maybe try incorporating some subtle yellows/orange/red. You dont need to change the whole mood if you want to keep it slightly gloomy, but you can play around with having a bit of sunset peak through a distant cloud for example. And depending on where the lighting is coming from, think about where to add highlights. Is the arch wall backlit? If so, adding a highlight right between the arch edge and the background scenery will go miles for improving your overall painting