heyyou

But really only if you're sure about your relationship.  

Its getting longer and longer, isn't it 😛

Your current timelines are a little off.
K1 is taking between 8 and 12 months.
CR1 between 12 and 18 months. 

Agreed 100%
From my observation, I use the more conservative estimate of 4 to 6 months.

You have only met once so a few more trips sounds a good investment.

For CR-1, you actually need to make a life together.  Not just APPEAR to have a life together.  It may mean your GF needs to come to your country to live for awhile, rather than just to marry.  
 
Do not do the B-2 fraudulent route.   You can get a permanent bar from the US for that.
 
None of the options will be quick, or cheap.  I suggest you read ad infinitum on these forums.  Best of luck!  :-)

Also gotta correct your timeline. 
K1 approval takes about 8 to 10 months. 
After the wedding in the US you do AOS and it takes 12 or more months to get a green card. Not 4 months. Just for the work and travel permit you might have to wait 3 to 6 months. 
 
Overall cr1 is better if you want to start working in the US asap.  Takes about 10 to 12 months for approval. 

I agree with that. As all people here who warned us about the attorney and  her suggestions, we will not work with her or won't follow her suggestions.
We appreciate the help we got from the forum 🙂Such an amazing community 👍

And just to chime in on the corrected timelines, even though it is completely out, the B1/B2 option is 12 months to a green card (5 or 6 to a work permit) so this lawyer is wrong on yet another front.
 
Avoid this person. They are either very, very badly informed or are steering you in a direction to make more money for themselves (make you think the B1/B2 to adjustment of status option is the best/fastest so  you'll choose it, knowing that you'll be denied the B1/B2 visa anyway, then you need to come back and pay them for more advice and more paperwork assistance for the visa you were supposed to go for in the first place). 
 
You'll meet people who have adjusted from B1/B2 visas. They were either already here and had a sudden change in circumstances that made them decide to stay or  (more likely) did not know that this wasn't legal and weren't caught or decided to take the risk and weren't caught. No one here can or will advise you to follow in those footsteps and anyone who does advise you to do that does not have your best interest at heart right now (there is an approximately 0% chance you'll get another B1/B2 visa at this point). 

Can your girlfriend support you financially for sponsorship? Her 2 children will be counted as her household even if she receives child support. With you, that makes a household of 3 (or more if she has relatives to support). Her income needs to be at least $25, 975 for 3 people for 2018, may be higher for 2019. Plus she will need to pay for your health insurance and other expenses.

This link has good info: https://citizenpath.com/faq/preconceived-intent-adjust-status/

The first option you gave in regards to the B1/B2 visa is considered visa fraud and no one will help you with that option here. Also after your removal I doubt that you would receive one anyway to be honest. 
 
K1 visa is the quickest option but also the more costly one overall. You have timeline wrong though in regards to this though. The current timeline is about 9-12 months to point of entry, you get married, file for AOS and get the Green card in about another 9-12 months. You can file for Advance Parole(AP) to travel abroad and the Employment Authorization Document (EAD) to work during the AOS process, those timeline are about 4-5 months after filing for AOS. 
 
CR1 visa is when you get married in your country and then she files for the visa for you. The current timeline is about 12-18 months overall. 
 
 
Personally I would do the CR1 visa if I were you. 

~~Moved to What Visa Do I Need, from IR1/CR1 P&P - The OP is trying to find out his options.~~
 
 
Your B1/B2  AOS thoughts ends now. This is clear visa fraud.  Not likely you will get another visa so soon. There is a record of you trying to enter with intent to adjust. If and a Big if you ever get another visitor visa you would have a very hard time proving doing this was not planned.  
 

A B visa is out. It would be fraud at this point.
 
I'm on my phone and can't see your country/consulate so cant comment on any difficulties you may encounter with a k1.
 
Aos from b Visa is out, so That leaves k1 or cr1. You are not under a ban, so neither will affect the petition. You may or may not have issues visiting here while one is pending. 
 
Cr1 would be my choice. Cheaper, not much longer time wise, and travel and work basically immediately. 
 
 

He doesn't have a country listed....

Dont talk to that attorney again, they are suggesting immigration fraud and should be disbarred
Thanks, dont usually pop on here on my phone lol

Yeah I would not go back to that attorney at all. Honestly at this point in time it looks like you don't need a attorney. 
 
You can get a B2 after you file fore the CR1/K1 visa but it is harder to get. 

A lot of proof such as pictures together, tickets and hotel receipts from spending time together. If you do the CR1 route then you will need to start trying to comingle finances. 

Go to your profile and click on Edit Profile, then where it says Country move the tab down to your country. This is to help give you better advice because some regions and/or countries vary information wise. 

Done. Thank you.
 
Do we have to have traditional big wedding for cr1? Or simple wedding is enough? Do we need to bring her parents to wedding in my country? Any other tips making sure that we have enough proof?

I help to try and KEEP people from making stupid mistakes lololol 😂