How can one combine prayers and perform tayammum or wudu at work in European countries, especially with the difficulty of prayer times and the unavailability of a suitable place for wudu or warm water?

Delaying the Dhuhr prayer until the end of its chosen time is permissible. Performing ablution with cold water due to the unavailability of warm water is among the deeds by which Allah erases sins and elevates ranks. As for washing the feet in the bathroom or an unclean place, there is no harm in it if the person performing ablution guards himself against impurity. Performing ablution in a clean place is among the virtues of ablution, not its obligations. The dislike of performing ablution in an impure place is lifted in cases of need and necessity. Therefore, the ablution is valid.