Help for newbie

[cornel93]

I have a Anycubic Kobra for like 10 days. First few prints were perfect (7or 8 pla 3 or 4 tpu), I am using Cura slicer with suggested settings (didn't change any of them in custom). Since 2 days ago I start to have some fail prints. I got some new filament (PrimaSelect PLA Chameleon) and when printing I've got some stringing and loose filament on hot bed. Tried to print some thin cobra skull bones and failed, changed to another filament (ESUN ePLA- Matte) print failed again. I changed few times the hot bed and eo temp but no success. Tried to print some bigger model and filament string broke (PrimaSelect PLA Chameleon). Can someone help me? Is it the filament bad quality? Is it because of Cura setting? Are the temp of the printed wrong?1st and 2nd photos- ESUN ePLA- Matte trying to print cobra skull bones3rd photo- PrimaSelect PLA Chameleon trying to print bigger model but filament broke4,5th photos- cobra skull bones