What's wrong with my sewing machine?

Hi everyone, my sewing machine is doing this—what happened? 

Hi Anja, which side is it? The top or the bottom?
It could be the thread tension—both top and bottom—so you’ll need to check that, or maybe you’re using the wrong thread, or the upper thread tension discs are dirty, or it’s simply threaded incorrectly.

Thanks, Akela♡
It was actually threaded wrong. I’d forgotten the second hook before the needle.
Tsk, I ventured to use the machine to sew masks with my rudimentary knowledge. 

Well then, if that’s all it was, it’s still okay :-)

I’ve been sewing masks now and have learned a lot. Just as high-quality yarn ensures great results when knitting or crocheting, high-quality thread is essential for sewing. In the past, I often bought those colorful boxes with lots of colors; the thread snags and slows things down. When I use brand-name thread, the machine runs like a dream.
Pressing well and carefully pinning the pieces together also helps immensely.
Every seamstress among you is probably shaking your head right now, but for me as a beginner, this is a very educational learning-by-doing experience.

Well, as the saying goes, “A well-ironed piece is half sewn.”

It looked almost the same on my sewing machine too. ☹ especially when I wanted to embroider
everything threaded correctly (several times), machine cleaned / problem still there
After asking at the craft store (which was very difficult because everything was closed, only by phone), I was told: wrong thread; come on, I’ve been using it for years / threaded wrongly; I’m not a beginner, I’ve been sewing for a while, but everything is correct / wrong needle; changed to a new needle several times / thread tension is O.K.
I found out that the bobbin thread keeps slipping out of the guide on its own... especially when embroidering with the cardboard bobbin (that was recommended to me by the craft store for embroidery)
The upper thread keeps breaking...... even with new needles

Does anyone know anything about this? What else can I do? Who knows this problem?

I have the Husqvarna Viking Diamond

For embroidery, you should only use this machine embroidery thread and machine embroidery needles; their eyes are smoother and not as rough as regular sewing machine needles.
Those so-called bobbins for the bobbin thread are nothing but trouble; I only use spools because I’ve had similar problems with my machines. For the bobbin thread when embroidering, I use overlock thread; it’s thinner and ideal underneath for embroidery.
Often, a tiny bit of lint gets caught in the tension discs of the upper thread tension, either from abrasion or because a thread has snapped; this often causes tension problems, so always check there too, and blow it out with compressed air spray
Unfortunately, I’m not familiar with the Viking; I have the Brother Innovis 3 as a dedicated embroidery machine, and I sew on a Pfaff Expression 3.2.

Thank you very much, Akela
I’ve always used universal size 90 needles from the start. I mostly embroider; after 3 to 4 embroidery designs, I change the needle. I’ll try special embroidery needles to see if that works better.
As for the bobbin thread, I also think the cardboard “bobline” ones aren’t the best. I’m already winding onto the other bobbins now. Overlock thread would be something to try. Thanks for the tip.
As for the upper thread, I’ll just have to check more carefully to make sure there isn’t any lint in it. But until now, I haven’t had to do that so often. Why now? 

The thread must be rubbing against something somewhere—take a close look to see if it’s catching on anything. That usually causes the thread to fray a bit, or maybe you just got a spool of thread that isn’t very good quality—it can happen, even with brand-name threads. All it takes is for the thread not to be seated properly in the upper thread tension discs—I know it’s all a very complicated interplay and can be frustrating.
But it could also be that the fabric you’re currently working with is causing the fuzz, since fabric quality can vary greatly.

It can’t just be the thread, otherwise I’d have several old, unusable threads. I have this problem with all threads, not just individual colors/threads.
I already know that this can happen with a thread that keeps breaking, that a thread can be bad... But several at once? Almost all of them?
The fabric could well be the problem; I often embroider terry towels and other very linty fabrics 😉

When you embroider looped fabrics like terry cloth or plush, do you place embroidery stabilizer on top of the fabric? There are washable and tear-away stabilizers you can use. That way, the thread won’t break, because this stabilizer protects the fabric, thread, and needle, as well as the embroidery design itself.

@Akela
Yes, I always use a film for that (AQUA Film—thin, transparent, water-soluble film) specifically for plush fabric. I place this film on top, and the embroidery stabilizer is underneath the plush fabric.