We see these often enough that they are worth mentioning here.
Thread loops on the bottom of the fabric
This is always caused by the TOP thread having no tension, or not being in the take-up lever. It sounds counter-intuitive, but it’s true, the bottom of the design is controlled by the top thread, not the bobbin.
Thread coming up
Usually this is a bobbin case tension too loose, or not having the bobbin thread in the tension at all. While it is possible that the top thread is getting hung up coming from the spool (very common actually) this usually happens in specific areas and appears quite severe. If you are seeing a lot of points coming up, it is usually the bobbin not having tension.
Machine-gun sound
It sounds silly, but yes, that rat-at-tap-tap can be annoying and even destructive to the machine. Usually this is your hoop flopping around when the needle rises out of the fabric. The needle lifts it up just a bit, then pops out, and the hoop flops down. It could mean the hoop is mounted wrong, is defective or simply a bad design. You can help by making sure you have a sharp needle, sized as small as you can for your thread. And you can try putting something on the arm of the machine to soften the blow. And definitely have it checked by a competent sewing machine service.