I'm having problem in pronunciation, what should i do?
Forvo lets you search for words and hear them pronounced by native speakers.
If you say the word along with Duo, regardless of whether or not it is a "speech" exercise, you will catch a lot of your errors.
For words that seem similar, I go to Google Translate and type in the two words, sometimes several times, and then click the speaker icon to have Google pronounce the words for me. When they're said "side by side" like that it's easier to hear what differentiates them from one another.
French pronunciation is really hard for me, too. I still don't have the hang of it at all, but those are the things that help me the most.