what is the difference between whether and if ?

how should i teach my students to have a better grip over english language ?

how to enhance my reading skills ?

what is the dif. between the usage of which and that ?

i don't know french at all.can sm1 tell me to start with it?

i have been good at english but in past two years i have lost my confidence .i want to enrich my english. what should i do?

what is the correct usage of word perhaps

is it right to say 'i don't know nothing?'