Will deleting the photoslibrary on my Macbook also delete the pictures on my iphone?

No (many iPhone users don't even have a Mac) -- but don't do that yet.

You want the pictures from your phone on your Mac, right? Then use iCloud. Turn on iCloud on your phone so that all your pictures will be copied to iCloud Photos. You may have to pay $3 for a month the get enough iCloud storage. If you like it, you can continue; if not, you can cancel.

The idea is to create a new, empty Library on your computer, and let it fill up from iCloud. You make sure all is OK, and then dump the One Drive copy.

And by the way, you can use a Library from a properly Apple formatted drive that's directly connected to your Mac, but you can't keep a Library on a network drive or any drive not formatted for Mac. You can see some details here:

Move your Photos library to save space on your Mac - Apple Support

You can create a new Library by closing Photos and then option-clicking on the Photos icon. A dialog opens that shows any Library that Photos knows about, which one is the System Library, and it give the option of creating a new Library, like this:

I have a bunch of Libraries.

Once you do that, you need to open Photos>Settings>General and check "Use as System Photo Library," since that's the only one that syncs with iCloud.

Then you should go to Photos>Settings>iCloud and turn on iCloud:

You see that I have "Download Originals" checked, but you can choose "Optimize Storage" if you are concerned about having enough room on your drive. If you use "Optimize Storage," then you shouldn't cancel iCloud!

Then you sit back and wait, maybe a couple of days, for the new Library to acquire all your pictures from iCloud. And when you're satisfied that everything has worked properly, you can delete the Library on OneDrive.

Let us know how it goes, and if you have questions....

Lemonsanni wrote: Hey! Thank you for your reply. Do you mean in the Launchpad? I tried that, but it simply opens the Photos app.

I never use Launchpad, so I hadn't realized that "option" does something different, there. Apparently Launchpad only launches. You can option-click Photos in the dock that runs along the bottom (or for me, along the side), or you can open the Applications folder and find the Photos icon there. While in OndeDrive, the Photos Library is useless to anyone.

If your are switching to Windows, then the photoslibrary will be useless on that computer -- it has to work with the Mac app Photos. The iPhone will still work with iCloud Photos.

So, you have two options: you can go ahead and create the Library on the Mac using the procedure we talked about, maybe using an external hard drive if space is a problem. Then you could have Photos export all the original pictures to Finder folders. (File>Export>Export Unmodified Original) You can transfer these to Windows, later. And if you have added editing or cropping or captioning to the pictures, then you need to also export the edited versions. (File>Export>Export nn Photos) to folders for transfer to Windows.

Another option is to download the pictures directly from iCloud.com to an external drive. You can do that on the Mac, or you can do it in Windows. But downloading from iCloud gets you the edited versions, which is probably fine.

I hope this helps get you there...

I have never used OneDrive, but usually it will not be possible to enable iCloud Photos while the local copy of your Photos Library is stored in a Cloud server like Google Drive, iCloud Drive, or One Drive. See: Move your Photos library to save space on your Mac - Apple Support

You will need to copy your Photos Library to a locally mounted drive, before you can open it in Photos. If you cannot copy it back from One Drive, you should restore it from a backup copy.

Do you have a backup copy of your Photos Library somewhere, perhaps as part of a Time Machine backup?