@Misbah you could start out with SimpleVectorIndex for now, it's easier to get setup.
Before thinking about langchain agents, I'd probably just try to get a simple version of gpt index working where you 1) load data into an index, and 2) query the index. See this notebook as an example:
https://github.com/jerryjliu/gpt_index/blob/main/examples/vector_indices/SimpleIndexDemo.ipynb.
You can just put .docx and .pdf files in a directory and use SimpleDirectoryReader