I speak 5 languages.
They are: English (native), French (C2 - high advanced), Spanish (C2 - high advanced), Mandarin (about a B2 - upper-intermediate), and Gujarati (about a B2 upper-intermediate.)
I was asked recently what my study routine is.
He asked specifically about what it was for Spanish, when I was learning it. Here is what I did.
High school - 2 semesters
Dabbled on free websites that taught Spanish for the first few months
Took two Spanish courses (one group class every day for 2 semesters + homework)
Listened to Spanish music all the time. I tried to tune my ear to the sounds of the language and looked up unfamiliar words in songs
University - 4 years
2-4 hours of group classes a day. These were mostly literature classes, but I also took some linguistics and general language classes
Daily homework and readings from my classes
1-4 hours of conversation practice a day with native speakers. I did this by going to The Spanish Centre at my university
Attended Spanish Meetups and events whenever possible
Listened to music and watched videos in Spanish. This was to tune my ears to the language and improve listening comprehension. It also helped my pronunciation and oral expression as I would imitate the native speakers I listened to
Travel abroad - about 3 months
Peru
1 week full-time lessons
2 or 3 weeks traveling with a tour group
3 or 4 weeks living with a homestay family + volunteering in a school
Chile
3 or 4 weeks living with a Chilean friend and his family
Overall it took me about 6 years to reach a high-advanced level.
It would have taken longer if I didn’t already speak French and if I had studied less intensively.
I wonder if a C2 is possible without traveling overseas. At this point in my life I don’t think I am up for traveling.