how to find more relevant keywords for Adwords campaign Keyword planner is not helping a lot

Keyword planner is hiding keywords, While spying on competitors I found they have a broad list of keywords than me that means they are generating more money.
I want someone's help or guidance to find more relevant keywords to increase my site revenue.
how I can found more and more keywords?
keyword planner suggests irrelevant and a lot of short 1-2 words keywords.
how can I found more long tail keyword?
Because in this campaign what we found long tail keywords are giving us more conversions…

how to find more relevant keywords for Adwords campaign Keyword planner is not helping a lot