Q1. What is verb tense(動詞時態)?

Tense is the characteristic of verbs that indicates the time

of  the action or state of  being  describes. 

Q2. How many tenses are there in English and how to use them properly?

There are twelve tenses in English.

 Simple Present　(現在簡單)

indicates an action happens regularly   

indicates a habitual action

indicates a thing true for all time

Simple Past　(過去簡單)

indicates an action happened at the certain time in the past

Simple Future　(未來簡單)

indicates an action happens at the certain time in the future

Present Progressive　(現在進行)

indicates an action is happening right now

 Past Progressive　(過去進行)

indicates an action that was in progress at a specific time in the

past, or indicates two actions in progress at the same time in the past

Future Progressive　(未來進行)

 indicates an action that is in progress at a specific time in the future,

or indicates two actions in progress at the same time in the future

Present Perfect　(現在完成)

indicates an action that began in the past and continues into the present (and may continue into the future) when since or for is used in the time adverb

indicates how long a present condition has lasted when for is used in the time adverb

indicates an action that happened at an indefinite time in the past

Past Perfect　(過去完成)

indicates an action that happened before a specific time or an action

in the past

Future Perfect　(未來完成)

indicates an action will be in progress at a specific time in the future

Present Perfect Progressive　(現在完成進行)

indicates an action that started in the past and continue up to the present, and usually not finished

indicates an action that has stopped very recently It is not happening right now, but you can still seethe result.

Past Perfect Progressive　(過去完成進行)

 indicates an action that was in progress before a specific time or an

action in the past.

Future Perfect Progressive　(未來完成進行)

 We look back on an action which has already been in progress from a

certain point in the future.                                      

If you have got all of them mixed up and found no way out, please try the chart in the sample set. It might help.