Is it worth buying a mixer or a sound card for me?

I do some music and often have latency problems. I use DAW FL Studio 20 and my microphone is the RØDE NT-USB. Although I use a high-end gaming laptop, I often crack and crackle while recording. Of course, it stops, but if I turn up the buffer size, then I can't record properly because the latency gets too big. For the following reasons, I have decided to get an external sound card or mixer, but they are not compact with USB microphones. Therefore, my question: "1. If I should buy a sound card or a mixer, I could then latency without cracking, etc. Sinks, so I would buy something at all bring?

2. How can I connect a USB mic to a mixer or sound card? (Without loss of quality but with gain)

P.S.: Sry, that I expressed myself so bruised, but I just have zero plan how to explain the situation well.

So your latency problems could have different causes and there are also different ways to get it under control.
A first simple factor is the memory of your computer. Under-working memory can cause massive latency problems, especially when working with many virtual instruments. But as I read from your description, you have at least a memory of 8 GB or higher (which is also needed).
Now for your first question. Buying an audio interface will definitely help you with your latency problem. Currently you are probably using the standard driver of your computer, which is simply a pretty latency by nature. An audio interface comes with a new, better driver, which gives you much better latency than you've got before.
Depending on what recordings you make, an audio interface also gives you the option of "direct monitoring", which allows you to listen to the recorded material directly via the outputs connected to the interface. This will save you the hassle of software and any delays. This is useful when recording live instruments or different microphone recordings. It does not help with recordings of, for example, Midi information for virtual instruments, since the "direct monitoring" is of course not possible.
Now to your second question:
There's no adapter to record your microphone via an audio interface. The reason for this is that your USB Mirko already has a built-in interface (so you can just connect and use it directly without having to have an external interface). That's just the advantage of a USB microphone, but at the same time can be a disadvantage. Then there's the question of whether it is vlt worthwhile to 1. Get a new micro and / or 2. How important your microphone is and you vlt. Prefer an interface even if it does not improve the situation with your microphone?
As a side note, there are of course other (small) ways to improve the latency, but in your case rather only provide a short term remedy to offer no solution, because they bring only small improvements and no decent interface / setup replace.

Thanks a lot, because I'm still attending school, I did not want to buy a new mic (besides, I'm very happy with my Røde nt-usb) and therefore connected my headphones directly to the microphone… And yes, I did not know that the Latency then less but when I tried it, I immediately noticed a difference. Thanks again, I can now record with a buffer size of 26 😁🙏