quälen
to torment
To intentionally cause physical or emotional pain to a person or an animal.
Es ist verboten, Tiere zu quälen.
It is forbidden to torment animals.

to torment / to struggle
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to torment
To intentionally cause physical or emotional pain to a person or an animal.
Es ist verboten, Tiere zu quälen.
It is forbidden to torment animals.

The verb 'quälen' (to torment) is closely related to the noun 'die Qual' (agony or great suffering). This connection helps you understand the intense and negative meaning of the verb.
Nach der langen Wanderung waren seine Füße eine einzige Qual.
After the long hike, his feet were pure agony.
The reflexive form 'sich quälen' means that you force yourself to do something or struggle greatly with something. It is often followed by a construction with 'zu' + infinitive or 'mit' + dative.
Ich musste mich jeden Tag zum Lernen quälen.
I had to force myself to study every day.
When thoughts or worries burden someone, the abstract feeling is the subject of the sentence and the person is the accusative object. So the structure is: something torments someone.
Die Ungewissheit über seine Zukunft quälte ihn Tag und Nacht.
The uncertainty about his future tormented him day and night.
In reflexive use, 'sich quälen' is often connected with everyday, unpleasant activities. Typical phrases are 'sich aus dem Bett quälen' (to drag oneself out of bed), 'sich zur Arbeit quälen' (to force oneself to go to work), or 'sich durch ein langweiliges Buch quälen' (to struggle through a boring book).
Am Montagmorgen quälen sich viele Menschen aus dem Bett.
On Monday mornings, many people drag themselves out of bed.
to burden / charge
'belasten' and 'quälen' can both describe that something is internally difficult for someone. 'belasten' is more general and fits worries, stress, or problems that create pressure. 'quälen' is stronger and more personal. It fits especially well when thoughts, questions, or feelings of guilt will not leave someone alone. 'belasten' often sounds more matter-of-fact, while 'quälen' shows more inner suffering. If something weighs heavily on your mind, you can use both, but 'quälen' feels more intense.

Die Frage, ob sie richtig entschieden hat, quält sie seit Tagen.
The question of whether she made the right decision has been tormenting her for days.
Heute belastet Milan der Streit mit seinem Bruder noch immer.
The argument with his brother is still weighing on Milan today.