Present Tense
Present Tense is used in Greek to either express regular actions, continuous actions being performed presently, simple actions being performed at the moment, or as a rhetorical device when telling a story about past events (historical present). Hence, it can most of the time be translated to English with the use of Present Simple or Present Continuous. (i.e. λύω can be translated as I untie, or I am untying)
The forms of the Present Active Indicative are as follows:
I.e. the endings (brown in the table) are added to the first principal part of the verb.
Reminder: The ν in brackets is a movable ν. It often appears before words starting with vowels or at the end of a sentence or a clause. But it can be omitted as well.
The forms of Present Indicative Middle\Passive are given in the following table (you can read more about the use of Middle and Passive voices here):
The Present Infinitive Active form is given by -- λύειν, i.e. ending -ειν is added to the first principal part of the verb. Infinitive forms behave as nouns and can mostly be translated directly with the English infinitive (i.e. λύειν -- to look).
The Present Infinitive Middle/Passive form is given by -- λύεσθαι. This can roughly be translated to English as to be untied.