Translation help

[voiceguy]

Hi there. I've been studying the newbie and beginner lessons for a couple of years now, but this is WAY beyond me. I coach actors how to do accents, and often have to get short bits of text translated and then I teach the actors how to say it phonetically. I've been asked to get 3 lines of a show translated into Japanese. Could you help me with these:

We only have tonight and tomorrow.

After that, it will be too late.

I’ll call you when I get to the museum.

If "you wouldn't say it like that" in Japanese, then how would you say it?

The level of formality is formal: it's between a couple of colleagues at work who are roughly equals.

Arigato gosaimasu! I appreciate any help you can give me.

Eric Armstrong

[mangara99]

Hi, here`s my try:

今夜と明日しかいません
konya to ashita shika imasen

その後、もう手遅れです
sono ato, mou teokure desu

美術館に着いたら電話します
bijutsukan ni tsuitara denwa shimasu

I'd like to tell you these sentences are perfectly written but I'm just a japanese learner too, sorry. I hope somebody checks them and do the necessary corrections.
Anyway I also hope this will be of use to you.