Powerbank for Toyota CHR

Hello dear community! My girlfriend owns a CHR Hybrid (Bj 2020) with which she regularly has problems. It happened more often now that she had to make use of Toyota’s Eurocare because her vehicle could not be started anymore. Sometimes he can not even open with the key. She was after each time at the contract workshop and left the car there for the first time a week, hoping to reproduce the problem, but everything in vain. The workshop repeatedly presses the key into her hand and says everything is fine. A change of the battery was not considered necessary and there are no solutions. The only suggestions that came were that she should drive the vehicle more or get a power bank to the start aid….Great tips for a vehicle almost costs 40 K. The problems with the battery usually came as soon as she was on holiday (10 to 14 days), but recently also after 3 days and my girlfriend slowly gets crying with the car. She usually drives four times a week to work and back again (each 30 min for 17 km) and sometimes smaller rides like e.g. shopping, washing a car etc.. A few times a year to her family in southern Germany. We have now brought a power bank for the purpose of starting aid (Flylinktech) and she had watched the last time as her Eurocare started aid, where the Lord has attached the clamps. After their vacation, we wanted to give a boost to the dead starter battery and realized that the cables are far too short to attach the places that Eurocare used to each other. We both are now little car-wandered and of course want to break nothing wrong and perhaps. All power banks at Amazon have such short cables, so I assume that you can attach the one used elsewhere as well as to the place used by Eurocare. The question is now, where do we fix the minus cable? My guess would be the screw in the “power box” at the bottom left, where the red cable leads. To illustrate, I added two pictures. One of the complete engine compartment, the circles are the places that Eurocare used. And a picture of the power box, where at least the plus cable comes in. We are grateful for every help.