The words are quite different. Do you mean the "th" sound in "truth" and the "ch" sound in "cheers"? I know "th" can be quite difficult for non-English speakers but one way to improve your proununciation is to keep listening to native speakers and and try and emulate the sounds they make. Not sure if that answers your question or if I have missed your point entirely.

bu ke qi. You're welcome.

Thank you so much Phil!! Your explanation is very easy to understand. I got it!

The beginning of “truth” sounds a little bit like hanyu pinyin chu. The beginning sound of “cheers” is closer to hanyu pinyin qi — especially in US English. As far as the final consonants (especially the th), you’ll need to search for a video or get someone to demonstrate it for you, preferably with video, or someone experienced enough to hear your tongue position and give accurate feedback. This page from the University of Iowa may be helpful — it uses International Phonetic Alphabet: http://soundsofspeech.uiowa.edu/english/english.html

Yeah, maybe after work I can upload my recordings. Thank you all for patience.