die Belastung
burden
A psychological or emotional strain or pressure that is experienced as heavy and unpleasant.
Der Stress bei der Arbeit ist für ihn eine große Belastung.
The stress at work is a major burden for him.

burden / load
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burden
A psychological or emotional strain or pressure that is experienced as heavy and unpleasant.
Der Stress bei der Arbeit ist für ihn eine große Belastung.
The stress at work is a major burden for him.

'Die Belastung' (burden/load) comes from the verb 'belasten' (to burden/load), which is derived from the noun 'die Last' (the load/burden). So the basic meaning is always that something acts like a burden or a weight.
Die ständige Sorge ist eine große seelische Belastung für sie.
The constant worry is a great emotional burden for her.
'Belastung' is very often used in the structure 'eine Belastung für jemanden/etwas sein' (to be a burden for someone/something). The preposition 'für' with the accusative indicates who or what is affected by the burden.
Die hohen Heizkosten sind eine große Belastung für die Familie.
The high heating costs are a major burden for the family.
In a psychological or emotional context, 'Belastung' is often combined with adjectives such as 'emotional' (emotional), 'psychisch' (psychological), or 'seelisch' (emotional/mental). It then describes stress or worries.
Der Lärm von der Baustelle ist eine tägliche Belastung für die Anwohner.
The noise from the construction site is a daily burden for the residents.
In a physical or technical sense, 'Belastung' describes a weight or a force. For example, people speak of the 'maximale Belastung' (maximum load) of a bridge or the 'körperliche Belastung' (physical strain) during sports.
Sportler müssen auf die richtige Belastung beim Training achten.
Athletes have to pay attention to the right load during training.
When it is about money, 'Belastung' is often used with the adjective 'finanziell' (financial). It describes costs, debts, or expenses that are hard to bear.
Der Hauskredit ist die größte finanzielle Belastung für uns.
The home loan is the biggest financial burden for us.
In an environmental or health context, the preposition 'mit' is often used to name the pollutant. Typical phrases are 'die Belastung mit Pestiziden' (contamination with pesticides) or 'die Belastung durch Feinstaub' (exposure to fine particulate matter).
Die Belastung der Luft mit Feinstaub ist in der Stadt sehr hoch.
The air pollution with fine particulate matter is very high in the city.
problem
'das Problem' and 'die Belastung' can both describe something that is difficult or unpleasant for a person. 'das Problem' refers more to the difficulty itself: something is wrong and you are looking for a solution. 'die Belastung' places more emphasis on the pressure that this situation creates for someone. So a problem can become a burden. If you are talking about the thing that needs to be solved, 'Problem' fits better. If you want to show that something takes strength or weighs on someone emotionally, 'Belastung' is more precise.

Die Pflege ihrer Mutter ist für Anna eine große Belastung.
Caring for her mother is a major burden for Anna.
Morgen besprechen wir das Problem mit dem lauten Verkehr in der Straße.
Tomorrow we will discuss the problem with the loud traffic on the street.