Usually a combination of the following factors:
Read about How to set the z offset
Level the bed with the SCREWS_TILT_CALCULATE
Try slowing down to 30mm/s.
First layer speeds depend on filament material and other factors. Speeds for first layers tend to be under 60mm/s and as slow as 20mm/s for some filaments.
No. Glue on a PEI bed plate is used to form a separation layer to prevent printed parts from binding to the bed plate.
Glue was used on older types of printers that had glass or other material beds than textured PEI which grabs far sticker than glue.
If glue is “working” for you then it's just sweeping the root causes of the poor bed adhesion under the rung and will still manifest as other issues.