"Dat was helemaal geen goed concert!"
Translation:That was not a good concert at all!
Likewise, "that was really not a good concert" was rejected, but the suggested alternative was: "...totally not a good concert". Although you can just about say that in English, it's rather niche and slangy. "Like, um, that was totally not a good concert." Have reported.
The use of "totally" in this context is, really, like totally a valley girl air head expression from the 1980s, like fer sure.