hi it's me again but stuck on different crossword lol. please help
12 across. portable megaphone. ?O?D?A???R
13 across. roman arena. ??P?I???A?R?
16 across. improve the quality of. ??R?C?
28 down. guess which is the highest. ??E?E?T???????
31 down. banner of the monarch. ?O?A?S?A?D?R?
thanks for any help very appreciated. xx