Hello Aroso,
may be:
Here "may" is a verb that means ' might'. It can be followed by any verb inclusive verb 'to be' as in ' may be':
It may be that = perhaps ,possibly
It may rain = perhaps or possibly it rains.
Maybe:
On the other hand is an adverb. It means also possible , perhaps and refers to something that has the potential to happen with an uncertainty.
" It is maybe raining today"
It means as well it is possibly going to rain , perhaps it is raining.
The main difference is in the sentence structure not the sense, the meaning is almost interchangeable .
'may be' and 'maybe' refer both to different sentence components.
Notice that when using ' may be' you are using 2 verbs and you can't in that case say for example :
" It is may be raining "
Here you would be using 3 subsequent verbs which is grammatically wrong in this form.
However you could say :
" It is maybe raining"
You are using the adverb "maybe" to describe the verb 'to be' .
So ' maybe' will be always used to describe a verb , while ' may be 'as 2 subsequent verbs form the predicate of the sentence.
" You maybe understand it "
Here the adverb 'maybe' is the description of the verb 'to understand' .
" You may be able to understand".
Here ' may + be' are 2 verbs in a sentence consisting of :
The subject : You
may be : verbs ( predicate)
able to understand : adjective + verb "to understand" in infinitive and both together " able to understand " forming the complex object.