can't drag and drop picture to photos from folder (macOS Mojave)

I'm using macOS Mojave on MacBook Pro, but now I can't drag and drop pictures from Folder to photos anymore. I have to import it from the "import button" (which is annoying, because sometimes I just need to add a specific pictures to album from the folder and doing it though import button is not convenient. Also import somehow works weirdly and doesn't import all the pictures from the folder. like I had 500 pictures, after importing it says I already have 25 of those on my photos and import all new ones 101. so where the rest of 474?!!!! It's incredibly annoying and inconvenient!