Nissan Kubistar (Baugl. Kangoo FC07) starts badly and lamp circuses when accelerating

my car is built in 2004, has only 78000 km and is still very good in general condition. It is a Nissan Kubistar and therefore identical to a Renault Kangoo FC07. 1. Recently I have problems starting the part. I read and read and at some point when I give gas the engine starts and runs without any problems – but when I start the vehicle on the slope it starts immediately. I tested the battery, checked the ground cables, the OT Geb he checks everything ok. If the part then runs, it is like if it is new up to 2. a certain point of the load independent of the speed – then comes the stop lamp, the pre-glare lamp and the engine warning lamp flashes. I then go from the gas and everything is out again. That is by the way a 1.5 dCi. Does one there advice ???? mfG