Good Morning fr. Vienna

it may be an easy to solve problem but, I cannot find a solutioin for my error on a just established portal with elgg. After Installation I could develope the site fine: with seldom plugins. From the beginnning I recogrinized, that uploaded pictures, used in blog and articels, group header after a while are not seen. After leaving the site and coming back during the (4) days the have been kept and are available/or not. I uploaded them now 4 times, now it is not possible to upload again. The page is frozzen. The 2nd problem today is, that after each admin action I get the message: Willkommen zu Elgg.
Redirect could not be issued due to headers already being sent. Halting execution for security. Search for more information." Also when logging in and out, uploading files; which are not kept by the system. Yesterday, last action has been to translate languages in german, for: Theme - Easytheme + event manager plugin + related group + group operator. I did not make my final decission to run the elgg community. But I like the structure, and do not need so much other plugins. I have to be carefully, bec. the more than 80 groups we will bring to the site are leaders of little museums and archives are older peoples and have to mantain their new communitys. When the site will be established and the groups accept it, we will engage a pro for site development. Though as a newby to this programm I need ahelp. I 've made a print out of the "system diagnostic"

Is there a developer in Austria I could contact?
Thank you for your help