Why should I ask for feedback?
Getting feedback is an important part of improving. It's arguably the most important aspect, as without it, you can get lost in the void figuring things out without the right knowledge. Getting someone knowledgable to playtest and/or look at your charts can be invaluable, and sometimes can even help you figure out something you've been stuck on for a very long time. It's extremely important to try and get feedback, and to take that feedback positively.
Where can I get feedback?
There are a few places you can get feedback, the most accessible of which is the charting channels in the Official Etterna Online discord, where numerous other experienced charters will look at your stuff and give their opinions. There's also a tried and true method of just submitting your charts to packs. Even if your chart gets rejected, the feedback you can recieve from that rejection can be amazing for learning what you did wrong!
What if I want someone to playtest?
Getting people to playtest your stuff is incredibly useful for seeing other peoples opinions, and thankfully there's a full sheet of volunteers who are happy to playtest and/or look at your chart in the editor and give you feedback! You can find them here!