Not bad.
The phrase 'no estar nada mal' in Spanish translates to 'not bad' in English. It is usually used as a slang phrase to comment lightly on a situation, object, or person stating that it's decent or somewhat good. It doesn't necessarily mean something is exceptionally good, but it's certainly not bad either. The use and meaning can vary based on the context, inflection, and tone in which it's used.
That restaurant is not at all bad for a casual dinner
This phrase uses the term 'no estar nada mal' to express the sentiment that, though the speaker may not consider the restaurant exceptional or super formal, it is sufficiently good for an informal dinner.
Your drawing skills are not at all bad
This sentence conveys a compliment to the subject’s drawing skills, using 'no estar nada mal' to express the idea that the skills are more than acceptable or even surprising.
Not bad at all considering it's his first job
This statement puts forth a positive judgment of a situation considering the established context, namely that for a first job, the subject's performance is 'no estar nada mal', meaning it is quite satisfactory.