Very sorry for your loss . I didn't have many friends my age when I was growing up but my Grandfather was my best friend . I trust that I will see him again one day and I am sure you will be with your Opa also. Knowing that makes being without him now easier to accept. Bless you and your family and I will be praying for you.
Eddie
P.S. YES, spend all the time with your Oma that you can . As much for yourself as for her . She will appreciate it now most especially and you will be glad of it down the road . Your time with all older family members is limited and is something you can never get too much of .