How much to charge for lost cell phone?

My colleague who lost my cell phone at the beginning of March and got it to me shortly before the beginning of June only wants to be liable for 200.00 euro for the cell phone. Is it ok or would you find it too little? It was a Huawei Mate 10 pro and important pictures and videos were saved in the safe that were lost. But he simply reset my cell phone which makes me angrier because I can't locate it! How much would you ask?

Lost? That sounds more like embezzlement. I would threaten the police. In such cases, the "replacement value" will be dealt with legally, whereby you can request a surcharge for the loss of your immaterial values (pictures).

even when resetting to the factory settings and using a different SIM card, you can track a cell phone using the IMEI number that is registered with every contact in the network.

I reported it because of embezzlement and so far no post or anything has come. What is the best way to proceed? Do you think a lawyer can help me with the value of the files? He took out the SIM card and then put it in his cell phone, he made it smart

And according to the police, the cell phone can't be traced at the moment. To this day it is still as if he had sold it somewhere in the shop

There's no upper limit of liability in the BGB. He is liable according to The current value of the thing immediately before loss.

and important pictures and videos were saved in the safe and were also lost.

Cloud?

The last sentence may indicate embezzlement.