question? structure

i'm ele level and have not learn characters yet. so i would appreciate reply/examples  in pinyin and translation.

[ni hai keyi yici fuqing bu]  my translation is > can you pay all at once (or in full)

my WB does not understand this sentence structure. why is 'ma' not used? 

 if . 'bu' is used in present tense is 'le mei ' used in past tense. is this way to ask a question necessary to learn at my level? and can someone give me simple example sentences?