What did you use to create the partition? Free space that is listed would be space that is not formatted or allocated in the partition table at all, it doesn’t really know if that space is available to take or is being used.
Also, having the partition (probably the entire drive actually since you’ll need to edit the partition table) mounted while you are trying to edit the partitions can cause issues.
It looks like the installer in the background of picture 2 is seeing sda6, what issue is it having, can you post a screenshot of that whole window without other windows on top?