Hi Loodz,
Take some pictures and share with us.
I had fix up some of those.
Clean up those corrosion and chemicals from the dead batteries,
and order replacement on ebay / aliexpress,
https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=battery+contact+spring&_sacat=0&LH_TitleDesc=0&_osacat=0&_odkw=battery+connector+spring
and some soldering skills.
if wire is badly damaged, you will need to replace it too