>>>>>2. During holidays your IQ level 'is going down' (zle) czy 'goes' (level-IT- 3os.l.poj - GOES) down?
'During holidays your IQ level GOES DOWN' when a message in the sentence is based, for example, on some research
or
'During holidays your IQ IS GOING DOWN' when you treat it as sth temporary, sth that will pass quckly, hopefully :)))))
it seems that using different tenses is sometimes very subjective and depends on what you want to convey, emphasise or on a wider context of your message