jetzt
now
Refers to the present moment; at this moment.
Ich kann nicht telefonieren, ich esse gerade jetzt.
I can't talk on the phone; I'm eating right now.

now
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now
Refers to the present moment; at this moment.
Ich kann nicht telefonieren, ich esse gerade jetzt.
I can't talk on the phone; I'm eating right now.

'Jetzt' (now) can be placed flexibly in a sentence. In position 1, it emphasizes the time and requires inversion (verb in position 2). Within the sentence, it usually comes after the conjugated verb.
Jetzt fängt der Film an.
Now the film is starting.
'Jetzt' (now) can also express an emotional reaction such as impatience or determination. In this case, it marks less a point in time and more a consequence or turning point.
Jetzt hör aber auf damit!
Now stop that!
When 'jetzt' (now) is used in contrast to the past (e.g., with words like 'früher' (formerly/in the past)), it refers not only to the moment but to the entire present day or era.
Früher war alles aus Holz, jetzt ist vieles aus Plastik.
In the past, everything was made of wood; now many things are made of plastic.
The expression 'ab jetzt' (from now on) marks a starting point in the present and looks toward the future. It means 'from this moment onward'.
Ab jetzt rauche ich nicht mehr.
From now on, I won't smoke anymore.
so / therefore
'jetzt' and 'also' can both introduce a consequence of a situation. 'also' usually clearly shows a logical conclusion: something is the case, therefore something else happens. 'jetzt' can also express a consequence, but it often sounds more strongly connected to the current situation or to determination. Learners can easily confuse the words because both can stand at the beginning of a sentence. If you really mean 'deshalb' (therefore), 'also' is often more precise. If you want to emphasize the new state from this moment on, 'jetzt' sounds more natural.

Der Bus ist weg, jetzt müssen wir zu Fuß gehen.
The bus is gone; now we have to walk.
Er hat den Termin vergessen, also ruft er im Büro an.
He forgot the appointment, so he is calling the office.