I have a work order question. The correct answer is listed as "We are not playing at the new building." which, I thought, would be in Hungarian "Nem játszunk az új épületńél." That is, the emphasis is that we are not playing (but rather doing something else). My answer was "Nem az új épületńél jászunk." which, I thought, emphasized that it is not the new building at which we are playing (but rather somewhere else). This is how I understand the English sentence.
For 'next to', you should use the postposition 'mellet'. It means physically next to and as opposed to in front of or behind, etc. In contrast, -nél/-nál is as much English 'at' as it is English 'by'. ("I'll meet you at/by the bank, not at/by the restaurant next to the bank." To translate into Hungarian, you would use -nal for the 'at/by's and 'mellet' for the 'next to'.)
Do you know German? Compare neben=mellet with bei=-nél/-nák.
I take it your question is about the use of English "by" vs. "at".
"At the bank" means in the same physical location as the bank itself -- most probably inside the bank or directly in front of it.
"By the bank" means within a physical location centered about or near the bank. "By" could be "at" the bank but could also be "at" any other point in the immediate vicinity.