Merging Cells in Excel

Hi, I have a big Excel challenge in front of myself and I hope that someone can help me with it. I have attached a file to better show you what I actually need help for.

Basically I have to merge those cells that have one and the same title/label. At the same time the values in each column for each pair of equal labels should be merged and summed.

Do you know an easy way to achieve this result?

Thanks in advance for your time!