Do you mean "tone" of English - as in speaking in a monotone, which means to keep the same sound level and minimize inflection? ("Tune" is related to music.) This could be tricky to change - there's no better way to fix this other than listening to native speakers and practicing. You could also try listening to English speeches and news broadcasts for examples of the way tone is used. I would suggest breaking up your sentences into pieces; using a "pause" (briefly stopping or perhaps taking a breath) between parts of sentences and where there is punctuation (like a comma, semicolon, dash, or period) may help.