Sucking thumb may lead serious orthodontic problems. Many can be treated well and nicely. Since I cannot see your pictures it is not possible to evaluate your case. However I strongly recommend you see an orthodontist ASAP!
Your upper tooth is in crossbite [tooth is behind], so best option is orthodontic/braces/aligner treatment to align teeth.
You can go for porcelain veneers but one tooth is in crossbite, so veneers is not recommended in your case.
for red gums visit the dentist for scaling/cleaning of teeth.
Black triangles between teeth are not a position issue, it is a shape issue. This is best solved with what is called Bioclear. This is a conservative method to fill in the spaces in a single visit.
