The main German word for “to visit”, the act of going to see a person or place, is besuchen.
Ich möchte dich am Wochenende besuchen.
I would like to visit you on/at the weekend.
Ich besuche meine Oma. I’m visiting my grandma.
Note that “besuchen” can also be used in the sense of “to attend”, as in a school or a course.
Besucher
A “visitor” is Besucherin (f.) or Besucher (m.)
Wir hatten letzte Woche viele Besucher*innen.
We had a lot of visitors last weekend.
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Besuch
“Company” (in the sense of “we’re having company”) is Besuch (m.).
Ich kann nicht. Ich habe Besuch. I can’t. I’m having company.
Besichtigen
Specifically for visiting landmarks in order to see them, the verb is besichtigen.
In Berlin kann man viele Sehenswürdigkeiten besichtigen.
In Berlin, one can visit many sights/places of interest.