is it possible to have 2 keyboard layouts at same time, with switching between them
by using hot keys (or tray icon)?
Yes, this should be possible with KeymapSwitcher. Here is a complete guide on how to install and use it, in case it isn’t self-explanatory: http://haikuzone.net/tips/hardware/using-keymapswitcher-switch-keymaps-fly
Hope it works well.