I see that young men can't get testicular cancer still unsure. Can young men at the age of 20 get testicular tumors/cancer?

Men from. Puberty through mid 30's are at peak age of testis cancer...Sayikng that, any age can get testis cancer and lumps and changes warrant exams. Disease is highly curable, and the earlier one detects, the less treatment. However, even disease spread to lungs and brain can be cured.
Cancer and boys. Yes. Cancer can develop in all humans despite their ages. But, the common cancer of the testicles does not develop in men until they are in their late twenties or early thirties. Other cancers are very rare in the young, but not impossible. On your next question about this please list specifically what you feel and any specific examination findings you see or feel.