First, you cannot merge partitions unless they are on the same physical device and are next to each other. For example, if your
sda is 320 GB, and you have an
sda1, then it is possible to merge these two.
Second, online services like Google Drive and Dropbox are not partitions. Currently, there doesn't seem to be an obvious way that space from these providers can be mapped/mounted locally directly. The current synchronization solution is to keep a copy of all files in cloud services locally, which ultimately takes your local space too. It is not possible to merge this kind of space with
I believe the best option for you is to merge
sda2 or any partition that is right after it. However, if
sda1 is the only partition you have on your
sda, nothing can be done to add space to it. One workaround is to add an HDD, and mount a partition on that drive (say,
sdb1) at some mount point where you have a lot of data, e.g.
/usr. You may want to refer to https://askubuntu.com/questions/656/how-to-move-usr-to-a-new-partition.