Hi Van Anh,
how to distinguish between landslides and subsidence is a question that relates to the interpretation of the results, not to the processing, so, it’s something beyond the scope of this forum.
About QPS processing, usually we consider it an advanced topic that one can tackle after having well digested more simple approaches.
Anyway, here the readings:
1. D. Perissin and T. and Wang, “Repeat-Pass SAR Interferometry with Partially Coherent Targets,” IEEE Transactions on Geoscience and Remote Sensing, vol. Volume 50, p. Pages 271–280, 2012.
2. D. Perissin, “Interferometric SAR MultiTemporal processing (techniques and applications)” chapter in “Multi Temporal Remote Sensing – Methods and Applications” Springer, editor Yifang Ban, ISBN 978-3-319-47037-5.
And more applied papers. You should be able to find them on Researchgate.
And then read the forum, like
1. https://www.sarproz.com/groups/sarproz-group/forum/topic/original-ps-method/
2. https://www.sarproz.com/groups/sarproz-group/forum/topic/mst/
3. https://www.sarproz.com/groups/sarproz-group/forum/topic/how-to-process-sbas-insar/
and many more.
About the analysis you did, I suggest you to contact someone via email, send a ppt with as many details as possible (dataset, area, processing options, partial and final results) and ask for a feedback
best