Very slowly inserts to db [требует правки]

I'm use MongoDB-3.4 WiredTiger and insert(List) and take result 1 million rec = 33s. If use single insert 1 million rec = 2min. But have problem with wery slowly inserts after every next million records (if use insert(List) of single insert):

• 2 million = 2m30s;
• 3 million = 5m0s;
• 5 million = 12min;
• ...

Please help me my e-mail: md5install@gmail.com My database must have bigger 1 billion records. And how to speed insert they. Thank you.