How to say "I go to see my sister"
If I want to say I gonna visit my sister. （我要去見我妹妹。）
Could I use like this ?
妹をあって行きます

Question

Answer

"I am going to visit my sister".

(Present continuous tense)

Answer

妹に会いに行くつもりです

verb + "に" + verb. Japanese often use this grammer.  It is difficult to explain but, it expresses a series of movements. for example,
会いに行く　会う+行く
食べに行く　食べる+行く
遊びに行く　遊ぶ+行く
In the same way, 〜に+verb is seen in " adjective + verb. here are some example.
好きになる　好き+なる
上手になる　上手（じょうず）+　なる
it may confuse you, but please try to search more if you couldnt understand.

Answer

妹に会うつもりです

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While two verbs beside using ”に”?
会いに行きます？

Answer

妹に会いに行きます