Please go to your Akeeba Backup Configuration page and scroll all the way down to the Fine Tuning pane. You will find an option labeled Maximum Execution Time. Select 14 from the drop-down. Click on the Save button and retry backing up your site.
If this doesn't work, please click on the Configuration Wizard button to let Akeeba Backup try to automatically determine the restrictions on your host and configure itself with the optimal settings. We know for a fact that Strato has restrictions on file sizes which are successfully detected (and worked around) by our Configuration Wizard. As a matter of fact, the number of our clients on Strato with similar issues was the reason why I wrote the Configuration Wizard in the first place.
Nicholas K. Dionysopoulos
Lead Developer and Director
🇬🇷Greek: native 🇬🇧English: excellent 🇫🇷French: basic • 🕐 My time zone is Europe / Athens
Please keep in mind my timezone and cultural differences when reading my replies. Thank you!