Ender 3 printing problems

A few weeks ago my ender 3 started to print poorly. I thought it was a problem with the hotend (because it had been stuck sometime) and yesterday I changed it and things have not improved.As you can see in the images, the first layer is no longer fine and as it prints, there are many threads (irregular, not because of a retraction issue, apparently), drops, etc.https://img.overpic.net/thumbs/p/b/j...is3vpcb_s.jpeghttps://img.overpic.net/thumbs/x/l/x...xgyk1ki_s.jpeghttps://img.overpic.net/thumbs/x/1/q...u4fyd6f_s.jpegA while ago I changed the original extruder mechanism for an aluminum one, I don't know if it may have something to do with it.Hopefully you can help me.Albert