Hi, Ramin.
We use “survival mode” to talk about a situation in which we have to work very hard simply to stay alive, or to find the things we need to stay alive. Sonetimes, we use this phrase figuratively, so you have to know the context to know exactly what someone means when they say they are in “survival mode.”
“To take every hour (or minute, or moment, etc.) as it comes” means to think only about what’s happening right now, because the future is uncertain and things are changing in every moment.
I would paraphrase this as “We are struggling simply to stay alive right now and we can’t think about the future.”
I hope this helps. Let me know if you have any questions.
-Danielle