I’m planning tofor my summer vacation.

My girl friend and I will visit to Hokkaido, where we haven’t go ne yet!

I have wanted to go to Hokkaido for a long time.

It’s because there are some historical facilitylocations, delicious seafood and great views.

Also, if we take a plane from Tokyo to Hokkaido, if we take plane, it’s almost onean hour and a half hour !

It’s so closely!!

I’m planning to my summer vacation.

My girl friend and I will visit to Hokkaido where we haven’t go ne before!

I have wanted to go Hokkaido for a long time.

It’s because there are somof the historical fbacilitykground, delicious seafood and great view.

Also, it's almost an hour and a half from Tokyo to Hokkaido, if we takego by plane, it’s almost one and half hour !

It’s so closely!!

My Summer Plans

Or you can say "My planned trip for this summer"

I’m planning to my summer vacation.

No need for the word "to" in the sentence

My girl friend and I will visit to Hokkaido where we haven’t gobeen before !

No need for "to". You could also say "where we haven't visited before"

I've wanted to go to Hokkaido for a long time.

It’s because there are some historical facility,buildings, they have delicious seafood and the view is great view.

You could have continued the previous sentence and just linked it with because, telling us why you've wanted to visit Hokkaido

Also, from Tokyo to Hokkaido, if we take plane, it’s almost onebout an hour and half hour !

Or you could say " from Tokyo to Hokkaido is about 90 minutes if we go by plane"

It’s so closely!!

I’m planning to my summer vacation.

My girl friend and I will visit to Hokkaido, where we haven’t go never been!

I have wanted to go to Hokkaido for a long time.

It’s because there are some historical facilitysites, delicious seafood and great views.

A facility is a bit of a technical term, it's a place that serves a specific purpose, in a dry/factual sort of context. E.g., restroom facilities.
Sites is a general catch-all that can mean almost any place of interest, and is often used in the context of traveling.

Also, from Tokyo to Hokkaido, if we take a plane, it’s almost one and a half hour !

It’s so closely!!

For exclamation marks, only one can be considered as correct grammatically. Using more than one is okay (and common) in text or chat, but it isn't "correct."

I’m planning to my summer vacation.

My girl friend and I will visit to Hokkaido, where we haven’t go been yet!

I have wanted to go to Hokkaido for a long time.

Since you're talking about something which started in the past and is continuing into the present, you should use "I have wanted" instead of "I want".

It’This is because there are some historical facilityies, delicious seafood and great views.

(1) "This is" sounds much more natural than "it is".
(2) "Some" means that you're talking about more than one of each of these things, so they should all be pluralised.
(3) "Historical facilities" is not wrong but does sound a bit weird. Maybe "historical buildings" or "historical sights" might fit better.

Also, to go from Tokyo to Hokkaido, if we take a plane, it’s almost one and half hour s!

Or you could just say "to go from Tokyo to Hokkaido by plane..."

It’s so closely!!