can i delete d: data and copy the files to c:

so that i have my 3 original partitions?

would this make it a little better?
Unfortunately this will not help. D: appears to be /dev/sda5 which is a logical partition

in your primary extended, you would need to also remove your primary extended, /dev/sda4

and here is the problem (well the largest one anyway, there are more), /dev/sda4 overlaps /dev/sda3.

/dev/sda3 appears to be windows C: deleting /dev/sda4 would also damage /dev/sda3

Your partitions (at least the ones with data on them) most at risk are /dev/sda3 and /dev/sda5

At a minimum, data you need from these partitions, needs to backed up, weather you install linux or not.

Your partitioning is a mess, don't risk data you need.